In the case of Japan, the only major political opposition not killed in the 1930s by the Right Wing Japanese Government was living in Moscow in 1945. The Japanese Right Wing WWII Government was more afraid of him than a US occupation. If the Soviet Union even had a little bit of Japan he would have a toehold and most organization still existed in 1945 (Through underground) and could be used to overthrow the Government. This was the big fear of the Japanese Government in August 1945. Thus the Russian invasion of August 8th, had a greater effect on the Japanese Decision to Surrender than the Atomic Bomber of August 6th and the 9th of August (And one of the reason for picking August 6th and 9th was that Stalin had Promise Roosevelt that he would attack Japan within three months of the end of the War in Europe, Russia said the War ended on May 8th, 2005 so Stalin kept his word by invading on the day three months after May 8th, 1945).
By August 15th in was clear to the Japanese that the US was NOT continuing its Atomic Bombing (It had been SIX days since the last atomic Bombing), but that Nothing was going to Stop the Russian Army from taking ALL of Manchuria by August 30th and maybe even all of Korea by August 30th (Through the more realistic date was September 30th). Once Russia had Korea, the main Communist Japanese Leader would only be only 123 miles away from the Home Islands of Japan (American Forces were 350 miles away from the southernmost Japanese Home Island in Okinawa). Simply put by September 1st, 1945 the Soviet Union would be in a better position to Invade Japan than the US would have been. The US had more supplies but the Soviet Union would have been three times closer. Now the Japanese did approach the Russians about Surrendering on August 8 (And received the Soviet's Declaration of War) but that was to start Negotiations between Japan and the US. The Russian intervention lead to panic among the Right Wing leadership. US Occupation was much more acceptable than even partial Soviet Occupation (and by August the Japanese knew of how the US, Britain and the USSR had divided up Germany). Thus what had in July been unacceptable, became the best option after the Russian invasion.
This continued AFTER the Surrender. The US did NOT want the Communists in Control of Japan, so kept most of the Right Wing Government officials in place (The US did execute some of the leaders, but most Japanese leaders below Command level were NOT even charged). During the time period of the US Occupation the US had one powerful hammer to hold over the Japanese Government, that it might pull out and put the Communists in Charge. The Japanese Communist Party was NOT large enough to take over Japan, but large enough rule if given Power. Thus the Post-War Japanese Government was NOT about to have the US Leave the COmmunist take over.
In Iraq, the Communist party has been dead for Decades (You do have its ghost floating around but it has very little political power in Iraq). The closest thing to the WWII era Japanese Communist power (In the sense of Political Power) are the Shiites (Supported by Iran). One of the US problem with the Shiites are its connections with Iran, but for right now the Shiites believe things are going they way and are waiting they time to take over.
The Kurds are another factor, de factor independent since Gulf War I, but viewed with suspicion by the Turks. The best comparison as to the Kurds with WWII Japan is Korea. Korea had been under Japanese Rule for Decades prior to WWII. That occupation was harsh (Just like Saddam's treatment of the Kurds). The Koreas hated the Japanese almost as much as the Kurds hate the Bathists. When Japan Surrender the US told the Japanese Commander in Korea to keep his troops in Korea till the Americans could provide replacement. Furthermore the US and the USSR came to an agreement as to occupying Korea to divide the Country at the 49th Parallel. The Japanese Commander responded that he could not THE KOREAN PEOPLE WOULD NOT LET HIM and furthermore the Korean People would welcome the Russian troops as liberators. If the US wanted Southern Korea the US had to provide its own troops, and had to do so soon or the Russians would take over all of Korea. The US rushed the troops into Korea to take over its half of Korea.
The same hatred the Koreans had for the Japanese, the Kurds had to the Bathist (and to the Turks). During WWII, The US, the Soviet Union and China were viewed by the Korean People as allies against Japan. In Kurdistan, the Kurds view the US as Allies, but the Turks and Iranians as enemies. Thus the Kurds are willing to fight the Sunnis, but also want to retain strength to be able to fight Turkey (and to a limited degree Iran). An important difference between the situations. During the Occupation of Japan Korea was ignored by the US (Till the Korean War). During the 1990s the US armed and equipped the Kurds but this was NOT viewed with favor by Turkey nor Iran. Apparently the Kurds have been willing to fight in the Sunni Triangle, the Kurds do NOT want to stay in that Triangle, preferring to fight for Mosul (and its oil wells). The Turks oppose arming the Kurds for fear that the Kurds will turn the Weapons on Turkey. Thus the only way to get supply to the kurds is by Airdrop via the Persian Gulf or ground transport via the Persian Gulf. Thus the Kurds are NOT a serious factor in the Sunni Triangle.
As to the Shiite, the Shiites are in South West Iraq (where the Largest oil wells are located). They look at the US Occupation as a chance to take over the Government AND the oil wells. Again NOT in the Sunni Triangle which is where the fighting is occurring. Furthermore the Shiites are tied in with Iran even more than the Japanese Communist Party was to Moscow in 1945. On the other hand the US is NOT willing to leave Iraq be ruled by Tehran even as an implied threat. Iran controlling Iraqi oil is worse than Saddam controlling that oil. Thus the US can NOT even use the possibility of turning Iraq over to Iran or the Kurds as a threat to the Sunnis.
My point that unlike Japan in WWII, the US has no hammer to hold over the head of the local Sunni politicians. Thus the revolt can go on and on. The US has to threat, bring back Saddam? That is what the Sunnis want so the answer is no. Leave the Kurds rule, The Turks will invade. Leave the Shiite rule? Not only will the US object to that, so will the rest of the Persian Gulf countries (Except IRan) for all of them are majority Shiite population ruled by Sunni elites (As to Saudi Arabia, the part of Arabia next to the Persian Gulf is overwhelming Shiite, while the rest of the COuntry is Sunni or a variation of the Sunni branch of Islam).
Given the above what do the Sunnis lose by revolting? In Japan in 1945 the Japanese Leadership saw if they continued the fight or went ot guerrilla war the only real winers would be the Communists. In the Sunni triangle the only will winners will be the Sunnis and the Bathist party of Saddam was Sunni controlled so Bathist/Sunni are almost interchangeable terms.
One Side Comment on the "Foreign Jihidists". Arab/Moslem world do NOT have the same sense of Nationality of the West. The best way to look at it is in terms of the Middle ages. If you were to ask someone living in 1200s in what is now Europe who he was, he or she would have said, a Christian, a Frank(In the sense he was a Roman Catholic from Western Europe), his or her occupation and than his Nationality. What we call National Identity or Nationalism is a product of the period since the end of the Hundred Year war in 1648 (Where one's religion was ruled to be decided by what prince you were living under, destroying the concept of religion being more important than one Country). While Europe destroyed the idea of belonging to something larger than one's country in 1648, that belief was kept alive in the Arab/Moslem world (and in Catholic Religious Doctrine to this day). Thus an Arab or Moslem views an attack on another Arab or Moslem State as an attack on his or her "Country". That "Country" being the Arab nation (and in terms of religion the "Moslem" Country). This is like a Frenchmen going to fight for Germany because Germany is part of his "Country". You see this concept all through medieval History, where people would show up and fight for other nation-states. In the Turkish Seize of Vienna the then Lutheran Swedes sent troops to help the Catholic Hapsburg's. The future Edward VI of England fighting the Baltic Prussians before becoming King of England. Emperor Frederick II leading an German-Polish Army against the Mongols. Even the Crusades can be seen as the "Country of the Franks" (i.e. Western Europe) fighting the Turks and Arabs.
While Western Europe has moved away from this concept of one's Country being larger than one's nation-state this is still a wide spread way to identify oneself in the arab/moslem world. Thus an attack on any Arab or Moslem Country will be viewed by many Arabs and Moslems as an attack on their own "Country". Thus these "Foreign Jihads" are viewed as foreigners by the US, in most of their own Nations and the Nations they are fighting in, they are NOT. They are NOT viewed as locals either, but fellow-countrymen. Comparisons can be shown in how the various volunteers from throughout the US showed up to help NYC after 911. These were NOT "Locals", but NYC residents also did not look upon them as "Foreigners". The same with the Arab Jihidist, the Sunnis of the Sunni Triangle do NOT view them as locals but do view them as fellow Arabs/Moslems.
For a time line on the Atomic Bombing:
http://www.nuclearfiles.org/menu/key-issues/nuclear-weapons/history/pre-cold-war/hiroshima-nagasaki/decision-drop-bomb-chronology.htmFor the 350 Miles from the Southernmost Japanese Home Island:
http://www.trumanlibrary.org/whistlestop/study_collections/bomb/ferrell_book/ferrell_book_intro.htm