Any Overnight Trains Besides Amtrak in USA?

Lots of 'em.  They are all freight trains.

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Yes, there are.

No.  In many huge cities - they may have trains, however, they are only Commuter Trains and NO overnight trips at all.

There are very few rail lines in the US that carry passengers other then AMTRAK. The few others are tourist rail roads or some times a rail excursion by an existing railroad. Often, if not always, these are day trips.

For example Cumbers and Toltec Scenic Railroad. Which used to run a train on an trip that went one way one day to a town and back the next. But not at night. It had an over night stop.

Traveling by night by train kind of defeats the purpose of traveling by train. I like traveling by rail so I can see the scenery.

The Trans U. S. Freight, Long Beach to NYC.

Simple answer is NO.

Freight trains run 24 hours a day on many rail networks.

AMTRAK is and has been the only passenger network for DECADES.

There are some commuter lines that have late night service but only go a short distance. HINT they do not need sleeper cars.

There are no passenger rail routes in the USA other than Amtrak.  The USA doesn't actually have a working nationwide passenger rail network, such as those that Europeans take for granted.  Amtrak just provides the appearance of one.  Americans fly instead, to cover the vast distances in a timely fashion.

There are a few excursion trains, but they simply look at scenery - they don't actually GO to any particular destination.