The United States has 12 million Jewish people, almost twice as many as Israel at 6.5 million, the only country to have more Jewish people than Israel. We also have the greatest percentage of Jewish people than any other country save Israel itself, with 3%. The next closest country is France at 1%.
That isn't to say that our approval of Israel has remained unchanged. We hit a low of 34% approval of Israel in March of 1979, around the time of the Egypt-Israel peace treaty. We also hit a high of 64% approval three times: early 1991 after the Manhattan assassination of a prominent Israeli-American Rabbi, early 2013 (after Hamas and Fatah show solidarity and the UN orders Israel to remove settlements to comply with the Geneva Convention), and early 2018 (after Syrians shot down an Israeli F16).
But US support for Palestine has slowly crept up over time, being 3-6% in the 1960's, up to 24% in 1988 (when Yasser Arafat declared Israel had the right to exist), and remaining in the high teens since 2013.
As for Europe, most of the EU countries have between 3 and 9% Muslims, compared to only 1% in the USA, giving them much greater exposure to Muslim peoples and cultures.