Even the relatively open "Great Plains" or the "Great Basin" provide plenty of fascinating terrain for guerillas to shoot up an unwary or tired convoy. You'd see El Salvador-style "toll booths" set up by the guerillas.
Like I said, government-imposed violence--absent a very deep commitment from all to the social compact, something that large-scale levels of authoritarian violence would destroy--becomes statistically ineffective in short order.
It's impossible for guerrillas to hide from FLIR etc if the rulers don't care about collateral damage (think Chechnya).