I am a radio operator, and those among us are prepared for just such an eventuality. Dial-up will be spotty, at best, since the government can control centrally-located communication media such as phone, Internet, and television, but they’re going to have a real hard time tracking down a mobile HAM or even someone on CB.
Larger stations with high yagis or VHF/UHF antennas might get shutdown for just looking like a radio station, so large scale broadcasting might not be immediately available; however, there’s a very robust relay network across this country that could ensure communications are available during a crisis, and I can assure you that many HAMs are ready for just this sort of eventuality.
The unfortunate part, like being an FFL holder, the FCC has records on who is a licensed HAM. If they wanted to round all of them up, that’s certainly a possibility, but the airwaves will still remain unregulated for obvious reasons. The government cannot be everywhere at once and cannot monitor or block RF coms everywhere at once.
Rallying points should be churches, community centers, schools, or even golf clubhouses.
Are there small mobile Ham radios on the market ?