I disagree. People who root for a team just because it is in their city will root triply hard for a team whose players come from that area. If you have one player on a team that came from the team’s home town, it is constantly mentioned. Imagine if they all did.
Problem is you’re missing the rivalries that already exist. If your region puts New Mexico together with Texas, especially if the stadium is in Texas, you just lost the NM market, they hate Texas they won’t be teamed with Texas. Same with SoCal and AZ. Try to get the UPpers rooting for teams heavily populated by non-UPper Michigan and Wisconsin and forget it. The country is filled with these regional rivalries that your 16 regions need to navigate around. Then of course you’ve got the problem of sports being a different level of popularity in different regions and drawing a different quality of player. You might get X-number of football high school students but if you’re in baseball or hockey country they’re not going to be the same quality as your Texas kids. That whole high school football worshiping part of the country will be better and win most of the championships, so competition quality just isn’t there.
If it was a more homogenized country it’s not a bad idea. But we are simply not homogeneous. It’s be a mess.