How can the rest of the world respond to such a state? We already know part of the solution, because the US has done it to those it has deemed "rogue" before: comprehensive trade and financial sanctions. Unfortunately, this is difficult when the US is the center of so much, but personal sanctions against regime members and their supporters are eminently possible, and likely to have an impact. The US has done this to ICC judges and officials in an effort to intimidate them into dropping cases against Israel and US troops in Afghanistan; but we can do the same to them. And it will hurt. Trump's a billionaire, he has money and investments all over the world. Ditto Musk, Bezos, Thiel, and the rest of his fascist cabal. We can take it from them. They will scream like Russian oligarchs if they can't access the money they've stashed in their foreign tax havens, or holiday in their usual places. And that in turn means internal pressure on the regime.
Longer term, its pretty clear that the US can no longer be trusted as a responsible member of the international community. Even if the current regime is overthrown and things return to "normal", it might happen again. Better therefore to reduce our dependence on them as much as possible. If we want a peaceful, stable world where we can just get on with our lives without fear of random attack, that world can no longer include the US.