Have you thought about partnering up with a US webmaster to send your traffic to some pages they host and splitting the take 70/30 or 60/40 with them? You getting the larger percentage since its your traffic? (allowing for huge amounts of BW of course... if that happened, take the BW useage off the top)
Putting yours or their banners from sponsors with unique ID codes to identify that they are hit from the traffic you provide.
