Again, thank you for the link, Dr. Whom.
The problem is not the lack of engineering know how. The problem is the cost. And that might be surmountable, if all four governments that need to be involved: American, Canadian, Chinese, and Russian chip in to initially fund the project. No the biggest problem (IMHO) is the lack of political will that is necessary. Especially now that the American government and the Chinese government are accusing the other of hacking into each other's computer systems.
I'd also like to know where the terminus is going to be in the U.S., as you also have the difficulty of obtaining right of way. I mean we can't get a pipeline built from Canada, which is right next to us, to the U.S. Though, alot of opposition to the pipeline is due to the fear of ecological damage that may occur, if there is an accident. And those fears would seem to be less with the railway.
As for the Chunnel, my favorite way to get to mainland Europe from the U.K., especially if I am going to Disneyland Paris. Just catch the train in London. One stop in Folkestone to pick up passengers and vehicles that are boarding the train from southern England. Next stop Disneyland Paris. And to return just reverse the trip.
One need not go directly to Disneyland Paris. There is also a train that ends in Paris, and from there you can catch a train or two to almost any place in Europe, including a local train that stops at Disneyland Paris. There is also a train that goes to Lillie, which I have never taken.
As for fears of an east-west invasion or a west-east invasion. They took care of that fear by mining the Chunnel, so in case of an invasion, the Chunnel can be collapsed in on itself.
Thank you again, Dr. Whom.