Renting a car in the US as a foreigner is not at all complicated, where do you get that from? It's one of the cheapest and best countries to do so.
I just spent 2 months in the US (California, Nevada, Arizona, Utah, Hawaii), had a rental car the whole time, drove around 4000 miles and it cost me about 6000 USD per month. While I'm not exactly living frugal the only way I see to do such a trip for less than 100 USD a day is camping on your own all the time. So yeah, most people just can't or don't want to afford that.