The Diomede Islands cut that distance in half. I’ve taken Shinkansen 🚅 connecting Kyushu to Honshu Island a dozen times in my lifetime shows that tunnels under the ocean are successful. The depth of the ocean in Japan is between the islands is 120 ft. Between Alaska and Russia at the closest point, it is 206 ft so it is very feasible
The Diomede Islands cut that distance in half. I’ve taken Shinkansen 🚅 connecting Kyushu to Honshu Island a dozen times in my lifetime shows that tunnels under the ocean are successful. The depth of the ocean in Japan is between the islands is 120 ft. Between Alaska and Russia at the closest point, it is 206 ft so it is very feasible
The ocean between alaska and russia vs japan is insanely different.