So Larry Kudlow, the administration’s chief economist (actually “economist,” but that’s another story) went on TV to declare that Trudeau “stabbed us in the back.” Peter Navarro, the administration’s chief trade expert (“expert”) went even further, repeating the stab-in-the-back line and declaring that Trudeau faces a “special place in hell.”

Remember when people used to imagine that Trump would be restrained by officials who would put some check on his worst impulses? Maybe that happened for a few months, but at this point he’s entirely surrounded by sycophants who will tell him whatever he wants to hear.

Still, America isn’t a monarchy — not yet, anyway. Congress has the power to check a president who seems to be betraying his oath of office. It can even remove him; but short of impeachment, there are many ways members of Congress could act to constrain Trump and limit the damage he’s doing.

But Congress is controlled by Republicans. And their response to a president whose actions are manifestly not just un-American but anti-American has been … a few sad tweets from a handful of senators who are unhappy about Trump’s behavior but not willing to do anything real. Most Republicans haven’t even gone that far: They’re just silent.

Why are Republican politicians unwilling to discharge their constitutional responsibilities? Relatively few of them, one suspects, actually want a trade war, let alone a breakup of the Western alliance. And many of them, one also suspects, are well aware that a de facto foreign agent sits in the Oval Office. But they are immobilized by a combination of venality and cowardice.

On one side, tax cuts for the rich have become the overriding priority for the modern G.O.P., and Trump is giving them that, so they’re willing to let everything else slide.

On the other side, the party’s base really does love Trump, not for his policies, but for the performative cruelty he exhibits toward racial minorities and the way he sticks his thumb in the eyes of “elites.” So any Republican politician who takes a stand on behalf of what we used to think were fundamental American values is at high risk of losing his or her next primary. And as far as we can tell, there is not a single elected Republican willing to take that risk, no matter what Trump does.

What all this tells us is that the problem facing America runs much deeper than Trump’s personal awfulness. One of our two major parties appears to be hopelessly, irredeemably corrupt. And unless that party not only loses this year’s election but begins losing on a regular basis, America as we know it is finished.