They are effective in non-developed nations where the population has known nothing but hardship and violence since the dawn of time. Anyone in the states who has the fantasy of it going the same for them, would be in for a rude awakening. We aren’t a hardened people like those who were born and raised in a constant stare of violence. As a whole, we are spoiled and sheltered.
Actually, there far more hard people here than you think and that makes unconventional warfare even more effective here where the majority of the population is soft (that part you got right)