The Tolkien Society has associate groups called smials and there are many in the US and Canada and Europe. I belong to one, Wellinghall Smial. We try to meet once a month, at least some members if not all.
I think the most active used to be Heren Istarion in NYC. But folks can check out the TS's page to see if there is a smial near them:
List of Tolkien Society smials. Contact info available through that link.
In addition to attending Oxonmoot and Return of The Ring, Downers can also make their own moots. Famous--infamous?--ones in the past have been Bostonmoot and Finlandmoot, and one summer the Finns made an entire summer of moots across the US. I was lucky enough to attend Niagara (Falls) moot. These mostly are organised on Facebook, which has a Barrow Downs group page.
Another way to maintain contact with other Tolkien fans is of course to join the Tolkien Society, which also has a Facebook page.