Fact is that the biggest Jewish populations outside Israel/USA live in Europe (1,5 millions), because they never moved.
The Jewish population in the US is much older than WWII and goes back to 1850.
Later immigration
The immigration restrictions of the late 1920s prevented many Jews from coming to the United States, yet some 100,000 German Jews did arrive in the 1930s, escaping Hitler’s persecution. During the Holocaust, less than 30,000 Jews a year reached the United States, and some were turned away due to immigration policies. Immediately after the Second World War, some Jewish refugees resettled in the United States, and another wave of Jewish refugees from Arab nations settled in the US after expulsion from their home countries. The last large wave of immigration came from the Soviet Union at the end of the Cold War, where approximately 150,000 Jews emigrated from.
http://en.wikipedia.org/wiki/History_of_the_Jews_in_the_United_StatesOf the estimated 8.8 million Jews living in Europe at the beginning of World War II, the majority of whom were Ashkenazi, about 6 million — more than two-thirds — were systematically murdered in the Holocaust. These included 3 million of 3.3 million Polish Jews (91%); 900,000 of 1.1 million in Ukraine (82%); and 50-90% of the Jews of other Slavic nations, Germany, France, Hungary, and the Baltic states. The only non-Ashkenazi community to have suffered similar depletions were the Jews of Greece.<19> Many of the surviving Ashkenazi Jews emigrated to countries such as Israel and the United States after the war
http://en.wikipedia.org/wiki/Ashkenazi_JewsSo of the about 3 millions Jews left in Europe only a minority moved to Israel from WESTERN EUROPE after the war. If there is only 1.5 millions left it depends of the emigration 1992-1994 after the collapse of the Soviet Union.