E.U.A: invasion and coup

In actual history, the United States has never suffered an invasion of guerrilla or a coup in its history... but what would have happened if it had ocurred one or both of those things? Does the United States could have remained the country's democracy?

Overview
In this alternate reality, the United States of America suffer an invasion by guerrillas in 1979 and then a group of military committed a coup in 1984, changing the historical development of the country and the Cold War forever.