They could do it

Some ambitious Chinese engineers are considering plans to build a high speed railway line that would connect China with the US. The undersea tunnel just to connect Russia and Alaska would be 200 kilometers (125 miles).

China is already in discussions and Russia has been thinking about this for many years. A project like this would require 13,000 km of tracks and it would take a train two days to make the trip if its average speed is 220 mph.

China has plans to build a high speed railway between the southeastern province of Fujian and the island of Taiwan. The trans-Pacific project, named the “China-Russia-Canada-America” line, would require a considerable feat of engineering. If realized, it would be the world’s longest undersea tunnel, four times the length of the Channel Tunnel, which connects England and France.

There are a few other ambitious high-speed railway projects. One project's rail lines would extend from London to Paris, then to Berlin, Warsaw, Kiev and Moscow, where it would split into two routes, with one ending in Kazakhstan and the other in China's Manchuria region. A second project's rail lines would run from Urumqi in China to Central Asia, then to Iran and Turkey, ending in Germany.

Construction has begun for both projects inside China, and the parts of both projects outside the country are still being negotiated with foreign governments.