First, Western Buddhists, from what I've seen, appear to be very dedicated. Since many have converted to Buddhism--they haven't inherited the practice from their parents--they are energetic and engaged, as opposed to (and this, admittedly, is secondhand information, as I have never personally travelled to the East) some of the more "going through the motions" Buddhists in many East Asian countries. What I mean by that is that you don't see many Western Buddhists praying to the Buddha for a salary raise. Western Buddhists, for the most part (and again this is a generalization) are serious about their practice and don't expect worldly rewards from it (in the form of gifts or good health). They don't try to butter up the Buddha the way many people do God.
A more puzzling argument is that Americans are "Americanizing" Buddhism. This strikes me as just self-evident. For some reason people think of Buddhism as an a-cultural phenomenon arising in an a-historical context. This is absurd. Take Zen, for instance. Traditional Indian Buddhism evolved into Mahayana Buddhism, which then took root in China, adapting into Ch'an, Pure Land, Hua Yen, etc. Why should Buddhism's migration to the West be any different? To disregard the fact that Buddhism obeys its own teachings of impermanence is foolish; it invites a kind of sectarian elitism, the old "I got the real Buddhism, while everyone else doesn't" mentality.
Zen is a Japanese form of Buddhism; it's what happens when you transplant Chinese (Ch'an) Buddhism onto Japanese soil, the synthesis of Buddhism and Japanese culture. And Ch'an Buddhism is how Indian Buddhism takes form in China. Many Westerners, in their attempt to stay "true" to Buddhist tradition, fail to see this.
The fact is that Buddhism in the U.S. will not look the same as it does in Japan or China, or anywhere else in Asia. Why? Because America isn't Asia! Why should we disregard all that the West has to offer--psychology, science, etc.--simply to preserve something which by its very nature must change?
Buddhism will adapt; it has for 2,500 years, surviving persecution, political upheavals, and foreign invasions. I think it can sruvive a culture of iPode and cell phones. But the only way it will thrive in this new soil is by adapting. Thich Nhat Hanh has been extremely succesful at this by recasting the form of Buddhism to suit the needs and understanding of Westerners. For instance, he offers a positive approach to the teaching of shunyata or emptiness in the form of interbeing or interpenetration. This is far from the watered down "Western Buddhism" that many skeptics predict or accuse the West of.
I like to think of Buddhism's migration to the West as possibly the final dissemination of the Dharma, perhaps the greatest one in history.
Photo, "The Western Buddhist Order of the Thousand-Armed Avalokitesvara," borrowed from Creative Commons flickr user: Triratna photos.