There are several aspects to it.
Israel has proven itself historically to be a major strategic asset to the US in the Levant, essentially winning the Cold War for the West in that part of the Middle East by defeating the Soviet-backed pan-Arab regimes and ultimately flipping the most important Arab state, Egypt, into the Western camp. They did this without getting US troops involved on the ground in the region, in contrast to, for example, East Asia (a couple of brief episodes in Lebanon excepted).
Culturally, the story of a beleaguered religious minority settling heathen lands and bringing the light of Western civilization to supposedly barbarous peoples is one that has, for very obvious reasons, resonated with Americans.
Throw in the oft-mentioned religious/evangelical angle, and the fact that the Jews have, by-and-large, been a success story in modern America with a visible and familiar presence in mainstream American society. Contrast with the Arabs and Islam, which in mainstream circles have tended to be mysticized and denigrated.