In the 80's, sure. The premise at the beginning of the first movie is that the dominoes had been falling for years.
Look at Venezuela. See any action at overturning that dictatorship? Look at our own government -- any sign of serious roll-back of socialist measures? Look at Europe -- see any sign of mass deportation of Muslims?
At each stage, an incremental victory for the Communists would be achieved, with them threatening total war at any attempt at roll back. Eventually they would be close enough.
Look amigo, how can millions of troops and materiel get transferred from one country to the next without being detected? Even if you could accept the absurd premise about the entire U.S. intelligence system being disrupted, there’s just no way a huge movement of military might could be transported without being noticed by larges amounts of people. I realize movies are exercises in suspension of disbelief, but the “Red Dawn” flicks strain that that belief to the outer limits and beyond.