OrigamiUSA is the American national origami society and the largest origami group in the world. It offers a lot of origami resources via their website, magazines, online shop and conventions. It’s not required to be an US citizen or resident to become their member. Their website has a link to other origami groups, both in U.S. regional and International.
Portland Oregon Paper Shapers is the local origami group in Portland, Oregon. It is a very casual group that meets once a month on second Sunday afternoons at Belmont Library.