It's absolutely nothing at all to do with the US economy (which, by the way, is in a bettter state than it was 2 years ago - the sponsors weren't leaving then). Example: Nissan are asking to have their name removed from the RSNT jerseys even though they have already paid for another year of sponsorship. Teams are having to fold because the sponsors have lost faith with USAC and the high-profile US riders involved in this mess. You don't see the "US economy" having an effect on other sports' sponsorship.