I know I'm a little late in responding, but I just wanted to share a few observations.
DH and I have just returned from a 2 week trip back to the US. I haven't been home since I moved here nearly three years ago, and it was his very first time. I'll second what a lot of people have said already...I felt like a foreigner. It was the little things, really. The way people tend to share their entire life story at the drop of a hat. The shock of having to pay sales tax (how I missed the good ol' reliable, no-surprises VAT!) and tipping. The birds--I, too, was fascinated by seeing cardinals and blue jays again--now weirdly exotic. The pleasure of having waiters and salespeople being cheery, conversational, and in one case touchy-feely. But as much as I enjoyed myself and loved seeing the family again (and especially playing tour-guide to my darling DH), I found myself anxiously awaiting our trip back home to the UK.
DH had a great time, lapping up the attention lavished on him by my friends and family. He's already saying he'll happily visit again any time. Granted, next time I won't wait three long years to return (hopefully) so maybe it won't seem so foreign. But this trip was the final confirmation that the UK is truly home now.