Could someone explain to a non-US resident why basically everything seems to be running on credit in the US?

You basically have money on a bank account (hopefully), but still lend with interest to consume?

The only credit card I own is from my employer for expenses, everything else is on debit. I only spend money I have. Quite a few people in Sweden, where I live, have some credit on their debit cards, but I think most people only use the credit for emergencies.