As somebody living in a "Nordic country", I respectfully disagree. The municipality often pays "volunteers" for this. It's usually sports clubs and similar organisations that need funding, and instead of just pouring it into them, the municipality "hires" them to do some cleaning, for example. So, after a big event in the city, you see folks all over the place cleaning up, often times kids from soccer clubs or such, but they don't do it entirely voluntarily, they do it because that will pay for their shirts next season or their trip to the training camp in the summer.
That said, it's also common to get involved in neighborhood activities that make things nice, planting some trees, painting some 300-year-old cabin in the woods with a bunch of neighbors that do care, this kind of thing, but I've lived in the U.S. for a while as well and we did that there too. Perhaps mostly with what you'd call hippies that participated mostly, but over here in $nordic_country, it's not like it's everybody who is contributing either. There are the more bourgeios who don't contribute and the I-don't-care-f*k-off type of neighbors as well.