Firstly: America's airports represent a minority of the daily commutes in America. In order for America's airports to be police states, they would have to be states. They're not. They're airports.

Secondly, while there are 'checkpoints' of sorts in NYC, I don't believe they're the variety staffed by heavily armed guards. I haven't been to NYC in around 5 years, but as I remember it interacting with police, heavily armed or otherwise, would be an extraordinary event on a daily commute.

Of course my definition is arbitrary, but I stand by it.