No one, probably. Industries and societies are complex systems and undergo elaborate evolutions, and when something goes wrong it usually is not due to a simple reason. However, we can speculate that it parallels what happened with the British automotive industry. In 1950 52% of world exports of automotive vehicles came from the UK. Today whatever is left of the industry is foreign owned. This video has Jeremy Clarkson's take on the problem.
It is a bit early to talk about the Sturgis Motorcyle Rally, maybe the largest in the world. But it is never early to point out that at the Sturgis Motorcycle Museum they have a 1948 Royal Enfield Flying Flea.