The Atlantic ocean is a big pool of water, and a lot of information doesn't make it from from one side to the other. The loss of information in the case of new and contemporary music is especially acute, and what is lost most is a sense of the bandwidth of the local musical cultures The music from a foreign shore which interests most is either going to be the best-marketed or the most exotic, and the vast swath of music in-between is mostly lost. Germany, for example, has not only a Stockhausen (a name known to many in the US), but a Rihm, a Lachenmann, and a Walter Zimmermann in various flavors of an avant-garde. But, with perhaps the exception of Henze, there is little awareness in the US of the large numbers of composers who write in more conservative or traditional idioms: a Killmayer, a von Schweinitz or an Enjott Schneider, a film composer (and the only remaining "serious" composer on the board of GEMA). Germany also has its own minimalism with Otte, Hamel, and many others.
The claim is made that by Johnson that European composers, are said to have a greater sense of their historical position than Americans. In fact, it's probably the Americans, who more often have to teach common practice theory and repertoire to pay for bread and butter, that look back the most. But tragically, for American music education, this "looking back" is seldom done with neither historical and ethnographic detachment nor the imaginative license that is our birthright. You want to learn orthodox music theory or history nowadays? Move to America. And Americans are said here to be individualists, composing ultimately for only their "own purposes". On this point, I have simply yet to see a significant difference between continents: both have their pioneers and both have their camp followers, both music cultures are enriched by the former and sucked dry again by the latter.
What America does have is that distance and license described above, and in particular, the possibility to approach music directly. For that reason, the most interesting music is inevitably going to be made away from conservatory and other large institutional settings, in which the program is to reduce distance and license from the European tradition. What American does not have are major institutions willing to support these most distinctively American impulses in music making, thus major orchestras program the works of composers whose ideas and techniques emphasize a competence with the technique of the received repertoire. We are thus in the odd situation in which a major American composer, someone who really brings something additional to the table, like Robert Ashley, has never had a significant opportunity to work with an orchestra.