You're kind of misusing the term federalism, I think. It generally applies in the US to moving power back from the federal government to the states, which actually seems to be in keeping with what you are advocating.

(it's strongest advocates in US politics have been people who are bitter about the federal government enacting the Civil Rights Act and stuff like that, so... have fun with your new friends)

Federalism has many meanings, but the basic concept is an association of equals or near-equals who make decisions by established protocols. While the US Federal Government was established in a time when communication could take weeks, by the mid-ninteenth century, communication was near-instantaneous, and many political thinkers tried to convince people that they could give up such a high level of representation in favor of mutual decision making based on systematic federalism. This was the beginning of the anarchist political movement, but it was widely dismissed by socialists in favor of traditional power hierarchies. Perhaps today with our even better communications infrastructure, we might be able to revisit some of these ideas of a more distributed power structure.

The loudest advocates in the US for federalism have been the nutty and frankly rather mean far right-wingers but it's worth mentioning that Noam Chomskyesque anarcho-syndicalism also involves some similar levels of decentralization.

The why and the how matter a lot in making that happen.

Power is so entrenched in the US that it's unlikely anyone will make significant changes from political office any time soon, but we can already see distributed power structures springing up in local neighborhoods that are underserved by their government. Detroit is a good example right now. People don't expect any help from the government, so they take care of things on their own and utilize community space to do it. When things get bad, people really have no choice but to be more self-sufficient and community's oriented.