I live in the US, but I cant change my Itunes store location.

I am Brazilian but I moved to America a few months ago. I dont have any american credit/debt cards but I would like to change the itunes store location to the US. Is it possible? When I go to Settings and try to change it, I am asked for credit card information, but my Brazilians cards are not valid. And of course, the information is required...

Please help :)