US financial transactions are overwhelmingly done by debit and credit cards. Cash is always an alternative. Paypal for mail xfers, though I dislike using it (it seems to be strangely popular with UK web stores for some reason, possibly due to usurious merchant account fees charged by British banks) is the norm.
But for web and face-to-face sales, credit card/debit card is the norm.
Only the Electric and Gas companies will take a check (proper US spelling since we are discussing US banking practice) and they typically process the transaction as a direct debit (the equivalent of getting a cheque cleared immediately through the aegis of the Bank of England).