I agree that Cincinnati is too small for another team. Hockey doesn't do well there.Based on the OP graphic:
Atlanta - It’s one of the top markets on the continent and can easily support a team. They shouldn’t be judged on what happened with an all-time horrible ownership group.
Cincinnati - Too small to have 3 major league teams. The team might survive but it would be a weak entry.
Houston - Absolute no-brainer, should have been done 50 years ago.
Kansas City - Similar to Cincy. A team could be viable there but it doesn’t feel like a 3-team market.
New Orleans - This would be a disaster.
Omaha - Just a bit too small. Omaha is a smaller market than Dayton or Rochester, which are obviously too small.
Phoenix - See Atlanta. Do it right this time.
Milwaukee - My only hesitation is saturation with the Bucks and Brewers. But I could see this turning up aces.
Sacramento - This is another sneaky smart one. There’s no reason Salt Lake can work and Sacramento can’t.
Markham
Hamilton
Kitchener - Combining these are they’re basically the same idea. I don’t think splitting the Toronto market is smart at all. Creating a White Sox or Clippers situation does nothing positive.
Quebec City - It just isn’t a major league city, and wishing really hard for it to be one won’t make it so. It’s a good emergency option if a team needs to play somewhere temporarily in a pinch.
In Milwaukee, you forgot about the Packers. We are still a home city for them after 30 years of no games here.
The City of Dayton has half the population that it had 40 years ago. The Dayton Flyers have that market sewn up!
As somebody who lived in SW Ohio for 22 years, I think that I know more about the Gem City and the Queen City than you do.
Rochester is similar to the above. The subway stopped running decades ago.