If people did not spend as much on their credit cards, they would have less debt (obviously). Today, many people do not have sufficient money to pay off their credit card debt, and this causes bankruptcy, which undeniably hurts the economy. Furthermore, many times, people shouldn't be buying things they do, therefore meaning that the debt they will accumulate has a larger negative value than the product they received has positive value, therefore destroying a fundamental idea in economics.
Yes, I think that the economy would grow if people minimized consumer debt on their credit cards, because people would have more money to spend on other things. They would not be spending all of their money on interest on credit cards. Only the credit card fat cats profit from this.
I do not think that the American economy would grow even if people learned how to reduced and minimize their credit card debts. I think that a lot of people are still going to either buy or save the same amount regardless of their credit card debts. Some people just don't change.
Unfortunately, the debt industry is a very profitable business in the US. Interest is what bankers count on to make their profits. Reducing the consumer debt would likely have detrimental effects on the economy because of this. The immediate effects would be detrimental, but the eventual effect may be positive. If that money saved on debt could somehow be spent on other commercial products, the money stays in circulation, just a new person is getting it, and the consumer is happier with the result.
To minimize consumer debt on credit cards, people have to pay down their balances which means they are paying money to the banks rather than using it on consumer goods in their local economies. While shrinking consumer debt is good for the individual, it is not good for the over all economy. The economy would grow more if people expanded their debt on credit cards.