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Top pick: NYC, it's got dozens of theater halls the convention center where Hololive has already appeared.
Boston would be my second pick.
Third, Chicago I guess. Then would be Texas, but you'll be more limited without a car.
Honestly, the issue is finding some place outside of CA that supports as many attendees as the YT theater did with 6,000 seats. Only major theaters and convention centers can go bigger, while I don't think cover can realistically rent out Yankee stadium or Fenway. But that would be cool if they did. Plenty of options if you're looking on the Eastern half of the country near a major airport.