Avery, Dogfish Head and Southern Tier are all american brewers. Cali, Delaware and NY respectively I believe.
Remember though beer was being brewed across the pond for quite a while before the USA was in existance.
Weihestephaner (German) is one of the oldest brewers in the world and although famous for their Hefeweissbier their Original which is a Helles Lagar is world class.
Duvel is probably the best beer in the world, its Belgian.
Plenty great stuff brewed everywhere in every style these days though.
I need to dry out a bit, get off the Tanqueray and Sailor Jerry so I can enjoy my beer properly again.