I believe it has to do with how much Americans tend to borrow, but I'm not sure which is cause and which is effect. Do Americans borrow so much money that they

I believe it has to do with how much Americans tend to borrow, but I'm not sure which is cause and which is effect. Do Americans borrow so much money that they need additional proof that they can pay it back (via credit ratings), OR, do Americans get the ability to borrow more because there are credit ratings systems to help lenders feel safer loaning money? Probably somewhere in the middle.