Besides Asia, I would say that the dim sum in NYC's Chinatown is the best out there. It's a tradition for many families and/or friends to go out to the restaurants and leisurely pick out these small delicacies from the ladies with the pushcarts.
Some places that I would recommend are listed below:
At Jing Fong Restaurant (on Elizabeth St., btw Canal and Bayard) you venture up an escalator, while looking at all the ornate chandeliers and intricate woodwork that they have. If it's your first time at dim sum, it really is impressive.
Golden Unicorn (on East Broadway) is a favorite for many tourists and locals.
DimSum GoGo (Chatham Square) is very tourist friendly. Here is the only place where they don't actually bring the dimsum out on the carts very often. After being seated, you get a sheet of paper which list the dim sum choices in English (which is a plus for people who don't speak Chinese) and you get to tally off how many of each item you want.
Golden Bridge Restaurant- (Bowery St, btw Bayard and Canal) is also want of the more ornate banquet halls in Chinatown. I find that here the portions are much bigger than usual.
Ping's Restaurant is also a favorite for many locals. It is located on Mott Street, in the heart of Chinatown. The decor isn't as elaborate as Jing Fong and Golden Bridge, but the food is still good.