The legal system and a stable non amish government keeps them safe. In a collapse they will sadly be overrun by desperate people who aren't pacifists and who use guns.
The history of the amish is being chased from place to place. I think they are admirable and very special, but they would not fair well in a period of serious instability.
Weren't they chased by state repression ? They would be in the situation where they're the most state-like entity. Or do you assume that they would stay pacifist and not use all weapons available if threatened ?
I think pacifism has been a core belief of theirs for hundreds of years, and they seem to be quite good at maintaining their core values despite pressure to change.
The history of the amish is being chased from place to place. I think they are admirable and very special, but they would not fair well in a period of serious instability.