Some years ago there were efforts made to establish Amtrak service to Las Vegas using Talgo trainsets. The Talgo company even built a trainset for the service at the same time they built the Cascade sets. When the service did not materialize the trainset was redecorated with a Pacific Northwest theme and assigned to Cascade service.
Yes, the big stumbling block was trackage improvements demanded by UP but, to be fair, the line East of San Bernadino sees a lot of traffic but is, I believe, largely single tracked. The other problem was an apparent lack of support in Vegas. It seems that the powers that be (casinos) don't see train riders as big spenders. They want to see people arriving by air.