Christian Science Monitor: Last year on the campaign trail, Barack Obama touted bullet trains as the next big thing in US transportation. “I don’t want to see the fastest train in the world built halfway around the world in Shanghai,” he said. “I want to see it built right here.” It’s an exciting prospect, the idea of saving US travelers time and carbon, and sparing them frustration over crowded highways and airports. But it’s a long, long way from Amtrak’s average speed of 40 m.p.h. to the magnetic levitation …