Coupling two things together in 200 or 300 kph is not a hard problem? That's like people without any programming experience saying, hey, that traveling salesman can be easily solved for 10 nodes, so just add more power and solve it for 100 or 1000, that cannot be that hard!
It's quite hard to control exact speed of a train (at such high speed), even without any atmospheric effects and with ideal adhesion conditions that never change. I can imagine it in like 50 kph, when the worst thing to expect is a derailment, some deformation zones blasted, and few non-fatal wounds. But every problem rises at least exponentially with the speed.