I'm a US citizen currently residing in China. Travel in China on today's modern China high speed trains is more convenient, comfortable, less expensive and far less troublesome than is flying. The actual trip may take a little longer, but even for long distances is quite acceptable; dramatically reduced time for check-in and security checks actually make up for the difference on shorter trips! (Security is quite equivalent to that of flying.)
Post-COVID, more ocean freight lines are now offering passenger options for long distance travel. Boats and trains are the best options environmentally, and should I ever decide to return to the States or visit other continents, it will be by boat. The notable exception is Europe: thanks to the expansion of Eurasian rail services between China, Europe, Laos and other regions, rail, the greenest mass transport of all, is now a great option for travel!