There are a few city pairs that are linked by Amtrak overnight, for example Pittsburgh->Chicago, Buffalo->Chicago, Omaha->Denver, Flagstaff->LA, Salt Lake City -> Reno.
As an aside, I used Amtrak to travel from Rochester, NY to NYC and it was totally weird when I asked people in Rochester (which has a population of about 200,000) for the train station. Most people literally didn't know where the train station of their city was! And it turned out to be as small as a regional rail or European sub-urb S-train stop. Only two platforms with no people on it.
Rochester Native here, and yep: I've never been to the rail station. Probably because the frequent, short flights to NYC are relatively cheap. Checking amtrak vs delta for a random date in january, your options are a 7-9 hour train ride for $54 in coach, or a 1hour flight for $64 in economy basic.]
For context: medium sized European city will have anything from 12-30 platforms - and often several main train stations and several dozen local ones in the city. E.g. Brussels, Paris or Berlin have several huge stations.