Regarding American drum 'n bass, I used to be really into dnb out here until a few years ago, when it just got beyond redundant for me.
I personally concluded that the problem with US dnb (produced out here on the west coast at least) is this American male obsession with machismo, competitiveness, and aggressiveness. Not that dnb from anywhere isn't filled with macho swagger, but the US stuff seems to be nothing but a dick size contest. I used to have this theory that the reason why Americans can't get over simple, dumb rockn'roll, and why our drum 'n bass is pretty much heavy metal made with breakbeats, is that we're a population rooted in the values of a mostly working class immigrant population, who have come to build a culture that values strength, machismo, stupidity, simplicity, speed, and straight-forwardness over anything we see as too intelligent, refined, "gay", or European... not that we're all that way, but it's definitely a big chunk of our culture. It's why we voted for Bush over Kerry, why we have to drive huge trucks, etc...
I'm sure there's decent stuff out there but I've moved on.