What is MLS? I don’t think you are talking about real estate listings.

I would say only bad players, because even they would be better than the colonial amateurs.
Anyway, sources, please.

Major League Soccer in the USA, @MollyMcGuire.

The USA has had increasingly more soccer clubs for children since the 1970s, so today’s generation has more people that have played soccer, which increases the appeal. In addition, there is a high number of immigrants in the US, who’ve come from countries where soccer football was the most popular sport. The internet and globalization of communications and media also play a part. Therefore, investors see this as a potentially growing market and are willing to pay big salaries to lure the players from other nations.

If they lure players from other nations it isn’t an American sport.

@MollyMcGuire – No one calls it an “American” sport, but MLS is the league of professional soccer teams which are located in the USA, about which the OP is wondering.

By contrast, basketball is considered an “American” sport, because it was invented by an American; but its professional league in the USA also recruits many players from around the globe, and many American players play for professional teams in other countries. Just as hockey, baseball, and soccer/football players earn salaries by playing for professional teams in countries other than those where they were born or have citizenship.