Comment by minkles
I don't disagree but if America distances itself now it will lose credibility, something which is somewhat low on the international stage at the moment. It has however done wonders for the defence industry here in Europe now we can't trust a traditional political ally. (This is not a criticism of the US, but a criticism of the UK and EU who should have military and political independence)
I think you miss that people tend to become less idealistic and further right as they get older. The "boomer" generation is just replaced by more of the same people. It's never going to change.
Defense of Taiwan is very important for the sort od reasons you're talking about. The defense of Israel though? That's a net negative which causes America a great deal of reputational harm around the world. With regard to Europe taking their own defense industry seriously again, I think that is ultimately a good thing for the American public, and in any case isn't caused by the trend of younger Americans disliking Israel. Rather, it is caused particularly by a certain baby boomer presidential candidate who simultaneously suggests that America shouldn't oppose Putin invading Europe AND that America should instead triple down on support for Israel.
As for people going "further right" as they get older, the younger American generations disliking Israel isn't a right/left thing. Young right and young left both dislike Israel, for their own reasons. Churches in America, particularly white evangelical churches from whom support for Israel is the strongest, are in a precipitous decline. They look like nursing homes now, younger generations aren't coming back and the boomers in those churches are in a panic over it.