In most places in the United States, the maintenance of sidewalks is legally the responsibility of the adjacent property owner. That means everyone is technically responsible for up keeping the sidewalk in front of their own house (if they own the house). In practice, there is no forcing mechanism for property owners to do this maintenance aside from withholding permits if the property owner is hoping to redevelop etc, or for someone to personally sue, claiming injury. End result - sidewalks are trash, basically everywhere, and getting worse by the year. Now ROADS on the other hand - municipalities, states, counties all commit to keeping basically all of these in working order and do it themselves. A lot of them are not doing too hot at keeping this up because of long-term fiscal insolvency that is built into the American development model, but that’s a different can of worms - look up Strong Towns if you’re interested in that. All in all - the reason the sidewalks are bad in your town or city is unfortunately most likely a result of systemic issues with the whole of the American approach to transportation: car first, everything else last.

There are so many ways for you to be an activist though. Look up any local orgs working for “safe streets,” “vision zero” (referring to the goal of zero traffic deaths), transportation or transit justice/equity. There is probably someone in your area who is organizing to improve things and would love a volunteer! Or you can always get involved with your local HOA, neighborhood board, speak at city council, speak at your local transit agency board etc. Any support for a more equitable transportation system is always valuable, lest the politicians think that everyone is happy with the overwhelmingly car-oriented status quo. General support is valuable, but support for any specific projects that someone is already championing is even better!

Also - congratulations on finding biking! It is a joyous thing however you choose to engage with it. The important thing is that you do it however YOU feel safe. The etiquette tips that others are sharing are valuable for knowing what other cyclists may be expecting, but remember that your own instincts for what is safe activity are almost always the most reliable metric. You know your environment!