I’m not as familiar with the laws regarding bikes as I am cars, but I suspect it’s a similar problem.

For many years US lawmakers have tried to help the US automakers (by help I mean they were paid handsomely for the help by automakers’ lobbyists) by creating laws that make it difficult for foreign automakers to get their vehicles into the states. For instance, there are laws governing how many models any foreign company can import in a calendar year. Surprise! Foreign automakers got around this issue by creating alternate labels, such as Honda & Acura, Nissan & Infinity, Toyota & Lexus, etc.

Similarly my bike, a 1985 Honda Shadow, is 694 ccs while the 1983 model is 749 ccs, because the US lawmakers raised import tariffs for all bikes over 700 ccs, as a way of helping Harley Davidson who were starting to get their butts kicked by the Japanese Big 4. Surprise! The Japanese makers just put a slightly narrower bore in the cylinders until the law expired.

Again, I’m not certain, but I suspect that similar issues are going on with the 125cc bikes that are available in Europe & Asia, but not in the states. The Shadow 125cc is another example.