Well, China's system is a failure, and he doesn't want the US to build trains, so ... it makes sense.
But something you have to keep in mind is the size of Japan versus the size of China and the US. The most popular Shinkansen route, Tokyo<->Osaka, is about the same distance between Chicago and St. Louis: a 6 hour conventional train ride, a 5 hour drive, or ... a 30 minute flight. So high-speed rail is kind of a hard sell: a 5 hour drive is not that long, and a 30 minute flight is worth the cost if you really need to be there fast. The middle ground, a 2 hour train ride, is not really that compelling, and a ticket would probably cost as much as flying. (The first time I took the Shinkansen, I had a little sticker shock. $200 to ride a train!?)
Rail does make sense for Tokyo to Osaka, though, because the airport in Tokyo is so far away from the city center. It's at least an hour and a half between Tokyo Station and Narita, and then you need to be there in time to navigate the terminal and board 30 minutes before departure. Then you have to do the same thing on the other end. So flying is a net loss between Tokyo and Osaka, which is why the Shinkansen is so successful. Lots of demand, and it's the quickest way to go.
But in the US, the places where high-speed rail will work already have high-speed rail. The other popular city pairs are too far apart -- New York to LA is popular, but that's going to be an awfully long train ride.