Unfortunately, there is nothing in the US system (as far as I can see) that prevents Trump-like behaviour being the new standard. There were three supposedly independent, contentious branches of Government. One is inert (legislature), one enabled Trump (SCOTUS) and the third, of course, is Trump. I am unaware of any mechanism that can change things.

Trump-like behavior isn't the inevitable result of the US System though. We could've had another 20 presidents in a row who didn't go and break the norm of maintaining global alliances and not threatening to invade our neighbors and closest allies constantly.

So it's relevant to ask if this would still be happening without Trumps antics, even isolationists like JD Vance wouldn't force our allies hands like this.

There is also the fourth - the press, which is either actively cheerleading him, or sanewashing every insane thing be does, or walks an eggshells around him.