Japanese aren't copying they are embracing an idea, comprehending it, and improving it. They could be inspired by anything, like any of us, but there has been much to be inspired by in the US over the last 50 some years. We all do this, but while americans focus on price per unit, Japanese focus on quality.
As I've mentioned elsewhere the subtle but powerful core difference between Japanese and Americans (quality vs quantity) form the foundation of two different emergent systems. Although it sounds simple it is a profound difference at scale.
This is why Japanese are very innovative, but most americans simply don't see it. Japanese had broadcast HD in the early 90s, and phones that could play TV 6 years before the iPhone.