Marklin have produced a number of F7 diesel locomotives over the years in A, AB AA and ABA versions. They have also done PA1 A and AB locos.

They have also produced a number of steam engines, notably Big Boy, Challenger, and Mikado (there may be others I don't remember).

For electric traction there have been the GG1 in a range of liveries, including Amtrak, as well as the ICE in Amtrak colours that was sent to USA when they were investigating purchasing high speed trains for the New York corridor. There is also a Swedish loco in Amtrak colours that was also a model of a prototype to get a contract I believe.

The Mikado and F7s have been produced in a wide range of railroad names.

There are a number of train sets with various of these locos, some with passenger cars and some with freight cars.

Most years Marklin have produced a selection of freight cars, often in sets of two or three cars, as well as singles. They have also done passenger cars as single cars, sets tend to come with a locomotive, but the single cars are designed with train consists in mind.

Roco for years had manufactured models for other brands, but mainly only in DC versions. The same was true for Mehano.
Roco did announce a few US models, but AFAIK they were never finalized.
MTH did release a number of modern US diesels in AC versions, but AFAIK that line was discontinued. You may still be able to find some models here and there.
You probably will need to do some research to find dealers who may still have these items in stock.

A search for MTH Wechselstrom would probably be a good place to start.

Regards

Mike C