Yes, the legal max is 4 watts, but that is if you're 'running barefoot' as they say, or without amplification.

There are car RF amplifiers that can run into the hundreds of watts or more and they do cause significant interference across many frequencies. CB radio users using these amps can easily be heard on home stereo systems, and sometimes even toasters (as lore goes, from their common use in the 70s & 80s).