Actually, an amazing number of containers go from the west coast to east coast by rail, the issue is there STILL isn't enough rail. UPS and JB Hunt gather stuff up and ship it to NJ on unit stacks
In fact, there are a surprising number of contains (due to changes in Customs) that go from China to Europe vis the following:
China to US west coast by ship (be it Oakland, SeaTac etc) and put right on waiting trains, which then run non stop to the US east coast, where they are offloaded from the train, right back onto a ship, and off to Europe.
I interviewed at a place that was deeply involved in this. As I follow the shipping industry (both a railfan and ship fan) it was a gig I wish I had gotten - sigh. Anyway, they are to the point they are totally automating the cranes, and the Rail Mounted Gantries (RMG) and Rubber Tired Gantries (RTGs) in the port, with humans JUST acting as safety overrides. They want to cut the turn around on the ships from like 72 to 36 hours if I remember the numbers right. Incredibly efficient operations, and as big a deal as the invention of the cargo pallet was during WWII (Yep - think about moving stuff around without a pallet )