Assuming we're talking about the 1984 original.
Red Dawn isn't quite a suitable analogy because it's about a foreign enemy invasion, not a civil war.
Despite our squabbles, it's a pretty safe bet that if the United States were to be attacked by a foreign enemy, unity would prevail.
It always has in the past, for better or worse.
Not only that but John Milius should be kicking himself because as it turns out, the United States "stands alone" alright, but not because of leftists, as indicated in the film's prologue:
As it turns out, America's allies are abandoning us because of actions by Trump and the Trump Right, not "leftists".
In fact, it's Trump that's attacking NATO and trying to dissolve it, not a bunch of lefties.
The Greens aren't taking over Germany.
AfD (Alternativ fur Deutschland - an extreme RW fascist party) is actually gathering power.
DISCLAIMER: My first wife's ex-husband was Red Dawn producer
Barry Beckerman.