Hey, I've lived in the US for 28+ years, and I don't think I could have named more than two MLS teams. They just aren't well known.
PS - I read the thread before posting, so now I know some of the teams. Before reading, though, I knew there were teams in NY and LA, but didn't know their names. I would have then just named the big cities: Dallas, Boston, San Francisco, Miami, Chicago, .... I don't believe Atlanta has a team. Ah, but there is a team in Denver, because my son lives there and has mentioned them.