Americans ranked foreign policy as the third most relevant issue for them in 2016, tied with immigration. [1] It's disingenuous to ignore that both parties have traditionally had mostly the same foreign policy stance. So you're voting for forever war, or forever war. How can it be a deciding factor for voters in this context?
But 2016 was different because Trump was the first candidate in some time to run on something even vaguely flirting with being anti-war, as he actively called out the endless wars of the political establishment, and argued that America first should not involve us wasting our money bombing countries half-way around the world. It was a relatively weak position but even that was enough to get 13% of voters to declare foreign policy as their key issue, tied with immigration. And Trump ended up winning their vote by an 18 point margin.
Anti-war is one of the relatively large number of issues that Americans largely agree on, but the political establishment makes it impossible to vote for, because you'll never find a mainstream candidate running on a platform that aligns with public interest. So for instance 84% of Americans think that "the American military should be used only as a last resort", that Congressional approval should be required for military action, and so on. [2]
[1] - https://en.wikipedia.org/wiki/2016_United_States_presidentia...
[2] - https://www.thenation.com/article/archive/new-poll-shows-pub...
