The only problem with the US is that there are only very minimal numbers of NFC terminals right now - even with EMV being mandated by 2016 most retailers don't yet even have EMV capable terminals. One would assume however that anybody replacing terminals now will have EMV + NFC support which is exactly what has happened in the rest of the world.
I've used Paywave probably half a dozen number of times in the US in the past year on recent visits and have pretty much had a "WTF" kind of look from staff, most of whom had never seen anybody actually use it before and were totally amazed by the technology. One wasn't even sure I'd paid.
We have a similar issue here too. People are aware of NFC technology and payments but it's difficult to find terminals that have contactless payment functionality, and even if they do you're probably at a cafe and the staff will just take your credit card and swipe/insert it on their end anyway.
On second thought though, when I have been using my phone to make payments recently I've been getting various wtf looks too lol.