Imagine if the Paw Sox were competing with the Mets, but the Red Sox could take the best player from the Paw Sox in the middle of the season. NYCFC isn't going to be on the same competitive firmament that other MLS teams will be on.
I like college football, but my team is far away. But since I want to go to games, I bought season tickets to the local college football team, which plays in a different league and sucks, but i don't care how crappy the team is, I want to go to games.
I used to live in NYC, and I have no allegiance to an MLS club. I like watching soccer, and my team is far away, so I would be open to watching live soccer here. I'm exactly the kind of person who they should be going after. But since I like Newcastle, I wouldn't root for NYCFC, since they are basically a farm team of Man City. Man U fans would be even less interested, and they are probably the most popular EPL team in the states. Mets fans wouldn't be interested since they don't like the Yankees. US sports fans intrinsically understand MLB/AAA dynamics, so anyone who understands that NYCFC won't control how they are run might lose interest.
Shit, if I was a Man U fan I'd start rooting for Red Bulls just to spite City/NYCFC.