Did you read the numbers carefully?
That is a selected list of countries. There are many that are unrepresented, including the countries that provided the vast bulk of immigration other than the FSU. So none of the Holocaust refugees (the Soviets didn't let theirs go, as you can see from those numbers), no one who came after the expulsion of Jews from Arab countries. The total for the USA and Canada combined is still only about 10% of the FSU alone. Did you really think Israel had so few immigrants in 1948? From 1948 to 1951, 120,000 Jews from Iraq alone immigrated to Israel under pressure from the Iraqi government. 50,000 came from Yemen in 1949-50.
At that the American figures are actually somewhat inflated because it doesn't track who stays in Israel. For logistical reasons, Americans (and some other nationalities) who don't intend to stay permanently may become citizens.
I wouldn't disagree that Americans are disproportionately represented amongst certain segments of settlers, but they are still very much a minority. Some settlements are known for active Anglo communities, but most are not.