Ha, I have a habit of wearing something Mets or Jets themed when I return to the US, because the very first time I was returning to the US, I was waiting in line (which wasn't exceedingly long, even) and one of the guys waved me over to his line. He said he was about to be done with his shift, but for a fellow Mets fan, he was going to squeeze in one more. Nice guy. We agreed if we ever ran into each other at Shea, I'd buy him a beer. (this sounds flirty, but it wasn't. more joking).
I've not really had any issues here. When I first moved over for work, they had JUST rolled out the T2s and they hadn't had a lot of training on them yet, so I had to wait for a little bit since one of the numbers was missing on my visa sticker, or something? But after about 20 minutes, it was sorted and they apologized about the delay. Usually I just get asked what I do for living. Once I got jokingly asked about stock tips but as this was in 2008, I just said not to invest right that second!