Would the VC try an ISIS like attack like that or would they try something which would affect the American war effort or the economy, like targeting water or power supply in the West Coast? I don't know, I'm asking.It's true that the Vietnamese-American community was vanishingly small pre-1970. I think this would actually make it easier for VC/NVA terrorists ITTL to infiltrate, because mainly nobody would be paying attention.
Let's say POD is July 4 1969. VC terrorists hit a 4th of July cookout/fireworks show in Orange County, gunning down 3 or 4 dozen civilians before themselves being killed. If it's absolutely confirmed as their responsibilty, I think Calbear's right. Nixon will order a 200-300 kt bomb dropped right in the middle of Hanoi.