Cards and cash
Visa and Mastercard are accepted everywhere; American Express slightly less so. Contactless payment is now standard. Carry some cash ($50 to $100) for tips, small vendors and emergencies.
ATMs charge $3 to $5 per withdrawal for foreign cards plus your bank's fee; withdraw larger amounts less often. Airport exchange counters have the worst rates; use ATMs or a no-fee card instead.
Costs
A mid-range day runs $150 to $250 per person outside the big coastal cities, $250 to $400 in New York, San Francisco or Hawaii. Restaurant mains are $18 to $35; museum admissions $20 to $35; national parks $35 per vehicle for 7 days (or the $80 annual America the Beautiful pass).