It's not the phrase "America First" on its own, but its history of use.
"While the America First Committee had a variety of supporters in the United States, 'the movement was marred by anti-Semitic and pro-fascist rhetoric.'"
And again, this is another example where they could have literally picked anything else... but they didn't. When pressed about its history Trump literally backed up the phrase's use by stating "I like the expression."
It's isolationist, nationalistic, xenophobic nonsense with a tinge of antisemitism. It's been denounced by multiple jewish scholars and the Anti-defamation league.
"While the America First Committee had a variety of supporters in the United States, 'the movement was marred by anti-Semitic and pro-fascist rhetoric.'"
https://en.wikipedia.org/wiki/America_First_(policy)
And again, this is another example where they could have literally picked anything else... but they didn't. When pressed about its history Trump literally backed up the phrase's use by stating "I like the expression."
It's isolationist, nationalistic, xenophobic nonsense with a tinge of antisemitism. It's been denounced by multiple jewish scholars and the Anti-defamation league.