This is close to 70 million alone (there are others) - Assuming everything else remained consistent, the candidate that carried these areas would win the election every time. The primary focus would then turn to these areas. This is a fruitless argument as getting 75% of the states to ratify this idea will never happen, and the only ones who want it are Dems, Republicans have far more states under control. Interesting points you make though, I honestly had not considered all those factors.

LA Metro - 13 million (+ 3 million SD)
SF - 7 million
Seattle - 4 million
Atlanta - 6 million
NY - 20 million
Houston - 5.5
Boston -6 million
Philly - 6 million