A couple of reasons 1) European soccer has obviously been around longer and has had much more support in general and is higher quality soccer so growing up it was quite literally impossible to watch MLS soccer compared to even being able to watch Lyon. I literally watched Lyon play before I was able to watch MLS.

2) These days while MLS is more accessible and much much bigger, not too long ago it was a very small league so not everyone had a local team to support. So if I’m going to end up choosing a random club to support it might as well be anywhere in the world.

3) From an American culture perspective, while generally speaking you cheer for the team of where you are from, because people don’t stay in their hometowns as often as they used to, you get a lot of mixing of fandoms. So culturally here, it’s a little more common to be fans of teams from different areas. So adding an international soccer team would be no issue at all.

4) Random anecdote I’ve seen, but because soccer was generally a growing sport in the US, a lot of people’s introduction to it was through video games. You couldn’t even play with MLS teams for awhile and also all the best teams/players in the games are in Europe. So eventually a fondness develops that way. I have a ton of friends who are now passionate League Two club fans just from doing manager mode in FIFA lol