Natural gas is dirt cheap in the US. Except in extremely dense urban environments with the physical plant already in place (NYC is the only one I can think of), it just would never pay back financially to use district heating. And if greenness/efficiency is the goal, using extremely efficient heat pumps and solar are probably a bigger win in most areas of the U.S.
My own district heat is also coming from a natural heat power plant, FWIW. I wager it's more efficient because they also produce electrical power (the heat is what remains in the steam after it's been run over the turbine to generate electricity).
I'm assuming by "municipal heat" you mean district heating. Can you explain why those systems keep getting rarer in the US? Over here in Europe, we are investing a significant amount of money in expanding those systems and connecting more houses.