America is in most cases not being considered as an 'avant-gardistic' country. Most people see America as conservative. I am of the opinion though that America is, in certain aspects, avant-gardistic. I would like to mention two things that could be called, in my eyes, avant-gardistic.
The first thing we could mention is America's movie industry, which is located in California. Take for example the movie The Terminator. This movie series can be seen as a (baroque) expression of our condition. The second one in the series is a great piece of art from the post-1991 era.
A second thing that could be called avant-gardistic is computer technology. Software engineers can be seen, to a certain extent, as an avant-gardist subculture. Many games, like Quake, refer to the uncertainty of the (post)modern condition.
Avant-gardism in Europe
The EU is not a progressive project. It is based on a central europeanist mode of thinking. It has "pushed away" the dynamism to places like Great Britain or Sweden.
It's remarkable why countries like France have let it all happen. It is a shame that Russia has to clean up the mess... again.