Hmm, are there actually any cities you are interested in visiting in a reasonable distance? Also keep in mind that you will be pretty much limited to the down-town area once you reach the town itself by train.
I think the big draw of these interrail train trips in Europe is that there are usually a lot of historic sites to visit in the cities, most cities are pretty walkable and that local public transport is also much better... I have a hard time to imagine this being the same in the US.