I'm honestly not all that worried about other cities trying the "Mamdani model"...
I'll explain why.
While I voiced concerns about Mamdani's economic policies...I explained that it was due to the fact that NYC is the seat of the financial sector, and certain taxes and regulations happening there can most certainly impact a lot of people who aren't in NYC due to the fact that almost all of us has some sort of account or financial offering with a entity that's in NYC (banks, investments, credit card, 401k's, etc...)
But a socialist running the city that's the seat of economic sector is the "worst case scenario" as far as concerns of that nature go, for reasons that are very unique to NYC, and that's already happened, he is the mayor elect, nothing can change that now. (Plus, a lot of NYC's stuff is still subject to state-level oversight due to aspects of their "limited home rule". So there are some damage control levers in place.)
A DSA member running virtually any other blue city has virtually no impact on anyone who doesn't live there, and actually provides the added benefit of giving the kids a real-world "history repeats itself" course in the kinds of policies that sound nice on paper, but fail in spectacular fashion when tried in the real world. (since a lot of the DSA support base are too young (or weren't born yet) to remember anything from the 80's)