Hi,
Just for information on how a credit rating is determined, here is a link with good explanations:
http://www.investopedia.com/articles/00/091800.asp
It is not just determined in the United States by having a credit card. There are 6 primary criteria, as stated in the link.
It's based on any types of loans one may have, or have had; including bank loans. That's why a co-signer can sign for a loan with someone having a bad credit rating, and if the loan is paid off, will help with the credit rating; with transactions by the particular bank or loan organization.