Absolutely untrue. Infact it couldnt be more wrong. Card is king. Pretty much the ONLY place you'll ever use cash is buying a drink at a bar or tipping somebody for carrying bags. Everything else - from a 50c soda upwards - is card. The fact they dont use chip and pin makes card usage even easier. For cheap stuff you just swipe and go...
On my last two trips to the USA I arrived with $10 in my wallet and withdrew perhaps $60ish from ATM's on a decent travel credit card over the period I was there. You just don't need cash. Card is king.