Red Dawn Scenario: Invasion of USA is impossible.
An invasion of the US is very possible.
Southern border with mass movements of populations tolerant of nomadic migration and minimal support.
A foreign power who has studied US tactics in the Iraq war,knowing how to route march and live off the land reinforcing their own route march with steady rapid speed.
Movements covered by a fifth column of native socialists who would betray the Constitution in a heartbeat and second any propaganda plan promoted by the foreign power.
Its a recipe for disaster, but in the eyes of a foreign power, might be more consistent with their soulish perception of righteousness in their own mind rather than ours.
The Red Dawn scenario unfolding is the one danger we face from the Old World and has been so recognized since the days of the Monroe Doctrine. The hubris that has led post-Cold War presidents to Eastern Hemisphere adventures has served us poorly by expending blood and treasure while ignoring more immediate and critical dangers starting at the Rio Grande.