Its a very well made, written, directed and acted movie, although there are a few low-budget mistakes.
The main problem is the supposition that a consortium of Mexicans, Russkies, Cubans and other left-wing statists could launch a successful invasion of the USA.
The movie seems to suggest that America was overrun pretty swiftly and everyone locked up.
The reality is far different than a handful of kids being the resistance. In reality an enemy would have to bleed for every inch.
The Mexicans have already accomplished a successful invasion of the US. Why does it surprise you?
Using Mexico as a staging area, plus having pre-positioned people in all the cities, it could be done. This was why we had the Monroe Doctrine in our country's early days.