USA has a large population of Jews. Not all are zionists, in fact there have been many anti-zionist Jews protesting against Israel's genocide of Palestinians. However, some are zionists. Some Jews see Israel as a backup plan - if shit goes south in the USA they can always flee there.
USA has a lot of evangelical Christians. Somehow (it's not in the Bible) they have convinced themselves that a Jewish return to the Holy Land is necessary before the end of the world happens. Which they want to happen, because they believe they are the good guys and will go to heaven.
USA has a lot of racists. They see Israel as an ethnostate, they like that and support it. Their hatred of brown people is stronger than their hatred of Jews so they are happy to see Israel oppress Palestinians.
USA also has anti-semites who are glad to see a place exist where Jews "should" go to. And they are ecstatic that Israel's genocide of Palestinians is igniting a new wave of anti-semitism.
Many Americans also see Israel as the only democracy in the middle east. It isn't a democracy, of course, since it has de facto control over Palestine and therefore a huge population is disenfranchised. But wait - rights only for a certain group of people, oppression for the rest - that's like America when it was "great" (ie pre-Civil Rights era) and they want America "great again".
You make good points - the reality is that most people whether in the USA or not are "apolitical" and have a surface-level understanding of things. Probably the thing to figure out is how that surface-level understanding is even formed. Those who DO have a strong opinion about things are more likely to be the ones trying to pull "common sense" or surface level understanding toward what they support.