Livio, all I can say is DON'T do it. August is very very very hot in much of the US. I can't imagine anything worse than traveling via bus or train at that time. The train service in the US is nothing like it is in Europe. Because our country is so large, most people fly to get from place to place.

Bus stations are often not in the center of towns or are in very unsafe areas. Please, please don't do this.

You could see some major cities by flying from place to place and have a much safer, more pleasant experience. If you list the places you would like to visit, we might be able to help you figure out how to do it. kayak.com is a good website to check airfares. How long do you have to do this? Would you fly home from LA?

What you could do is a combination of flying and driving.

It would be a tiring adventure, and as others said, I don't think you'd save much.

Buses and trains in the US are nothing like those in europe. Buses are generally used by people with minimal income and unlimited time. There are no hotel stops - just buses and bus stations (usually at the worst end of town - and some places out west in the middle of nowhere - a truck stop/gas station).

Amtrak is better (but stil nothing like trains in europe) - but it doesn;t reach many places at all and is very often late. (The train tracks are owned by the freight conpanies and freight trains take priority - Amtrak trains have to pull over until they pass and then follow them. Trains being 4 -6 hours late is well known.) Also - Amtrak will cost just as much as flying - if not more.

Except for certain short sections of Amtrak (from Boston to Washington DC) the only really efficient and economical ways to travel the US are flying and by car.

You are much better off trying to get an air pass in europe - or to fly longer distances and then rent cars to do sidetrips from various cities.