[@NecroKnight]
Powerful nations whose civil society collapses don't lose their military power overnight.  I can't think of any historical example where that has been the case.  The Russian Federation still haz a strong military and extensive nuclear arsenal to this day despite being the product of the USSR peacefully collapsing.

And the US has tons of inertia going into this.  All those bases didn't get nuked after all.  The war didn't escalate that hard- it just had a war with a rogue state and a invasion launched from Japan that got rebuffed with China alienating the whole world by destroying everyone's satellites.