Heck, less than half of Western Europeans would fight to defend their own country[0]. In the UK, only a third of people surveyed would do so. That's less than those who believe that the US would come to their aid!
Irrelevant. This measures trust towards USA to send their people who are willing to fight implied by them joining the military, not willingness to fight amongst the general public.
I don't think the blame is on America here.
[0]: https://www.gallup-international.com/survey-results-and-news...