The USA ranges from budget-friendly to extremely expensive depending on location. New York and San Francisco are among the world's priciest cities. Mid-range destinations like New Orleans, Nashville, Phoenix, and most of the Southeast offer much better value.
Budget travelers spending $80-120/day outside major cities can manage hostels/budget motels, grocery store meals, and public transport or ride-sharing. Driving is often the most cost-effective way to travel between cities — car rental plus gas can beat Amtrak (which is slow and unreliable between most cities) significantly. National Park passes ($80/year) cover entrance to all US national parks and pay for themselves quickly.