The best US beer WAS...
Gorky's Russian Double Imperial Stout.
Black, rich, with a chocolate cream finish and a hint of bitter in the nose.
Unfortunately, this old time Downtown L.A. eatery (est. 1907, and added a brew-pub in the mid- 1980s) tried to expand into "fashionable" Hollywood trade with a second location...and went broke in the 1990s.
A great pity.
The best "commercial" beer is probably either Sam Adams Cream Stout or Anchor Porter.
YMMV