There are, or have been, US several sites which have tried to do the same thing as we've got here. However very few of them seem to have been able to get to grips with the problems of moderating posts. (This site has active editorial staff and about 30 volunteer moderators, including myself, who try to get rid of all the rubbish). So they tend to end up full of spammers and trolls.
The Answerbag.com is case in point. It was closed down because it was full of spam and trolls but then bought out by new owners, who promised to sort the problems out. However the spamming and trolling quickly resumed. (I've not checked it out recently though).
One might have thought that the mighty Yahoo could do better with answers.yahoo.com but that also has its fair share of troubles.
The only US Q&A sites that seems to be well run are Quora.com, Answers.com and StackExchange.com but none of them seem to be as easy to navigate as this site is.