Hey!
I'm from Potomac, MD (in Montgomery County), not too far from you...I'm in London at the moment, freshly dropped off from the Argon Events tour to Wacken. It wasn't cheap going to Wacken, since it's right in the thick of prime tourist season, but it was worth every f'ing penny, I thought! So I'd definitely recommend going next year if you can manage it.
There weren't many other Americans that I know of at Wacken...I met one guy from New York who said that he'd found two other Americans...but that's about it.
My dream would be to put together some sort of organized trip for Americans to go to Wacken next year...I'm sure it would be a logistical nightmare though, and I'm not even sure how many are willing to endure the cost (and work, haha) of making the trip...who knows...