Tree cities are a good place to start, but they often have enough trouble enforcing the ordinance on their own trees, much less those on private property. I feel what you do on your own property ought to be your own business, unless it affects the public safety. So a topped silver maple two feet off the sidewalk? I have a problem with that. Telling someone that the city says they can't top that same tree in their backyard seems wrong to me. Sure, they topped a tree and ruined it, but it is their property, their eyesore and their maintenance problem.
I work with several small communities aside from my regular line of work, and the plain fact is that most of them are clueless about tree care. They know what their uncle/grandpa/cousin told them 25 years ago and they've done it that way ever since. Try a little volunteerism - ask to sit in on a tree board meeting - every tree city is required to have one. A few hours worth of talking in the right ears goes a long way towards the future health of your cities' trees. Putting them on the right track costs you little, and while you're not changing the whole world you're improving your part, or at the least buying it time.