I just moved to the US from the U.K. and am interested in a Sunday league or something like that.
I’m assuming you mean an adult league where you pay to play. There are many levels depending on where you are. I’d do a search for ‘adult (or men’s) soccer league’ for the area you live. You should find something.
An adult recreational league is basically Sunday league in the United States. Check for adult football/soccer clubs near you, and see the prices. Keep in mind, not only 18, 19 and people in their 20s play, you will find people in the 30s playing.
the USL and the NASL.
Recreational league or rec league. There’s an indoor facility in Toronto: they have ‘rec leagues’ that are men (by age group) and a co-ed league.
Just join a football club I guess. Or ":soccer": seeing as it’s America.