Nationalism, of course, has been pretty much scorned or denounces outright by every President since Reagan, and our immigration system has been self-destructive since 1965, when Ted Kennedy's bill welcomed everybody on earth to immigrate except Europeans.
But when you win, what happens? Everybody wants on the bandwagon. All the neverTrumpers among the Republicans want to join up somehow with the Trump administration, even as they attempt to undermine its policies. Some, of course, "sincerely" join up, meaning that they put on Trump's policies like a new pair of shoes, ready to discard them when it becomes prudent to do so.
But that's not entirely a bad thing. That's the way political movements work. In 1860, there was a whole spectrum of opinions concerning slavery, emancipation, recolonization, nationalism, federalism, states' rights, etc. When the war broke out, there were only two positions of note — unionism and secessionism. Right now it's gelling into Trump and anti-Trump. The middle ground is disappearing as its inhabitants move one way or the other.
The danger to us is that Trumpism will be diluted by the same old same old from the Republicans and the faux conservatives among them — McCain and Graham are particularly egregious examples. This would of course diminish the Alt-Right and replace it with the Alt-Lite, which, as Thrasymachus puts it, is just William F. Buckley all over again. Buckleyism of course wrecked conservatism, largely by purging its ranks of some of its most effective thinkers, such as Sam Francis and Joseph Sobran. Pat Buchanan was among the last to be thrown under the bus by Buckley.
And here's what Thrasymachus has to say, from his site here [link]: