How fat everyone is. You get used to it in the States, but when you first return it's the most immediate thing to notice. Second thing is the amount of billboards.

The prescription drug commercials

I've spent 3 years in Japan, 4 years in the UK, and a year in Korea. For me it was how incredibly rude everyone is. Sure I encountered rude people in other countries, but it's on another level here. Also, there are so many bad drivers that drive so confidently here.

Edit: typo

The size of the meal you get a restaurant and how cheap it is. I knew it was big and cheap, just forgot to what degree.

How much personal space people need. I also need that much personal space, but I thought I was just being unfriendly

Road width! There's so much room for activities on american roads compared to the very narrow side streets in most european towns