But how can they use that military to stop tens of millions of people spread out throughout the country from making tiny incremental changes in their daily lives (to use mainstream services, products and platforms a little bit less each day)?

Separation does not necessarily mean waving a new flag or physically drawing a line on a map. It can be far more subtle and diffuse than that. And the people who have "dropped out" don't actually have to be geographically concentrated in one area. That may happen later (slowly) but it doesn't have to start that way.