I think the issue here is that the data is not coming from the FAA primary / secondary feed, which can be blocked.

Instead the feed comes from the hobby / enthusiast crowd with a receiver hooked up to a PC, much like the scanner crowd feeds ATC VHF or Rail radio traffic to the web.

If you have Mode S transponders with the ICAO 24-bit address it identifies the aircraft.

If I recall there is an out for GA with Mode S to get a pseudo 24 bit address. I don't know where the cutoff is, MTOW, Turbine..... etc. where this is not an option.

The ACARS feed is big in Europe, this won't go away.

ADS-B has a more aggressive rollout in Europe, this tracking hobby will grow.