Stop saying Trump is like Brexit!
James Wrigley

One addition and one disagreement:

You mentioned differences between the electorates for Brexit and the upcoming American election, but another big difference is that Brexit was a referendum. A single issue, yes or no. Issue referendums are especially vulnerable to demagoguery, and sometimes turn into referendums on leaders.

By contrast, the American presidential election is about many things at once. Winning requires building a large coalition, and voters who may disagree with Clinton on one thing (e.g. foreign interventions) may vote for her because they prefer her position to Trump’s in other areas (taxes, stop-and-frisk, whatever)

(I wrote more about this here, if you’re interested)

My disagreement is with your claim that Trump is a new phenomenon:

Trump isn’t that new, and Trumpism is older still. Trumpists just haven’t had a champion at this level before.

And, since it’s not new, it’s not going away, even if Trump loses badly.