It's going to require action that's outside the bounds of government at this point, seeing as how all of our institutions are now active enemies of the nation.

Realistically you stop it by gathering a sufficiently large force of men with the conviction to actually defend the border and have them do so through force of arms. The real question is whether or not the institutions can be forced into actually performing their duties to the nation and that I don't know how to accomplish. That said, I think if you saw a force of 10,000 American men actively repelling invaders on the border and the government rolled in and put it down by force, you'd be hard pressed to cover it up and the optics of the government actively stopping people from defending the country might be enough to get some of the peasantry riled up enough to notice that their government was an enemy to the nation.

Not sure that would actually work though. The problem has been allowed to fester to the point where there are no good solutions left on the table. Helping the barbarians to invade doesn't strike me as our best option however.