What ad banner networks market to non-US traffic?

i'm losing out $$ because of all the defaults

[skunker]

Hey folks,
I have a website that gets 6 million pageviews a month, however, half of my traffic comes from non-US countries! I'm losing out on making money since Tribal Fusion (my ad network) only sells to US visitors. So, what can I do to fill my defaults as a result of this non-US traffic?

Thanks for any tips!

[Quadrille]

Adsense banners. Valid the world over, but takeup does vary. Do a test for a month.