Germany is that way to a lesser extent. I know my German friends visiting the US find it very odd that people who do not know each other well (or at all) will greet each other when passing by. It seems superficial and fake to them.
I'm from the Midwest and I find NYC and LA to be incredibly alienating for that reason. I'm surrounded by people but none of them acknowledge my existence. If I'm walking around my own downtown almost everyone who passes by will nod or wave or say "nice day isn't it?" just to be polite.
I held a door open for someone when I was in NYC last time, which turned into a big mistake. Everyone else hadn't been paying attention and when they saw me holding open the door they must have assumed I was a doorman and everyone flooded through the open door not giving me the chance to catch back up to my group. Meanwhile in the Midwest, if someone is a few steps behind you and you let the door close, they're going to be complaining about how rude you were for hours.
To a lesser degree, I felt that way after moving to Southern Californa from the East coast: https://pbs.twimg.com/media/Cvzm3sZWAAETO_b.jpg:large