Football has a pretty decent following in Canada, and a surprisingly rabid fanbase in Japan of all places. It's not at NFL levels, but they do enjoy the sport there.
The issue that many Americans have with soccer is that it's an amazingly low-scoring game, the players have a reputation for flopping, and the offside rule prevents one of the most exciting plays in sports, the breakaway. I will say the constantly running clock is nice, though ending the game in a draw is cheap. Allow for some more contact (or let the flopper get carded instead), tweak the offside rule to allow for breakaways, which drives up scoring opportunities, and end the game with overtime or shootouts.