Considering how splintered the US is in ideology and how much paranoia it has toward "foreigners" (which in reality aren't necessarily foreign and are almost always people who don't pass as white) a war with the entire world would likely turn into the US doubling down on that paranoia and on white supremacy and start hurting its own citizens en masse before a single other country has set foot there. Add to that the severe drop in functionality and amenities from being cut off from the world economy and everything they outsourced. The rest of the world would show up one day to see what's going on and the US would be Mad Max. Profoundly disturbing country to live in.
It would be like Mad Max combined with Nazi Germany's worst atrocities, or perhaps better compared to the worst horrors of the Ustase. But if you ask me, just that fact alone- that the US and other Anglo settler-colonial societies would certainly spiral to such depravity when given an excuse, and that the minorities and in particular the rightful indigenous peoples of the land live constantly with their lives hostage (and with "quiet" genocides continually being maintained to this day) is reason enough for why the rest of the world will likely have to take a role in decolonizing the Anglosphere, one way or another (presently, while it's not indigenism which would be better, I'd argue the foundations for such a process are being built, somewhat, with the demographic decline of white Anglos in these countries).
Considering how splintered the US is in ideology and how much paranoia it has toward "foreigners" (which in reality aren't necessarily foreign and are almost always people who don't pass as white) a war with the entire world would likely turn into the US doubling down on that paranoia and on white supremacy and start hurting its own citizens en masse before a single other country has set foot there. Add to that the severe drop in functionality and amenities from being cut off from the world economy and everything they outsourced. The rest of the world would show up one day to see what's going on and the US would be Mad Max. Profoundly disturbing country to live in.
It would be like Mad Max combined with Nazi Germany's worst atrocities, or perhaps better compared to the worst horrors of the Ustase. But if you ask me, just that fact alone- that the US and other Anglo settler-colonial societies would certainly spiral to such depravity when given an excuse, and that the minorities and in particular the rightful indigenous peoples of the land live constantly with their lives hostage (and with "quiet" genocides continually being maintained to this day) is reason enough for why the rest of the world will likely have to take a role in decolonizing the Anglosphere, one way or another (presently, while it's not indigenism which would be better, I'd argue the foundations for such a process are being built, somewhat, with the demographic decline of white Anglos in these countries).