I can understand that, though I feel if D.C. (excluding a proposed FD) becomes a state, I could definitely see arguments being made that NYC or parts of California becoming their own states. People would of course argue that D.C. is unique, but given how perception drives reality, I know a lot of people from upstate NY or the conservative parts of California that would very much like for their politics to not be driven by a major populous metropolis that they feel may not have their best interests at heart.
Well the difference between DC and NYC and California is that that DC has been since its inception a separate entity from Maryland and Virginia. Prior to the founding, there was literally nothing there. It was only and ever only a large chunk of George Washington’s private estate. In fact DC’s exact location is derived because Washington used his influence to use the federal government as a piggy bank in exchange for his worst property. And when it was set up, it was set up to be independent of the surrounding territory.
So the development of Washington DC can only be understood as an independent polity from Maryland and Virginia, despite its proximity to either. It’s had an entirely different governance from them. And the call for statehood is really more the territory pointing and going, “Hey, we have more people than many western states. What gives?”
To split New York and California though would be much funnier.