Fun fact: the Mars bar is marketed as a Milky Way in the U.S. There was a Mars bar in the U.S., but it had almonds. It has since been rebranded as Snickers Almond.
American here; you're spot on. The US/Mexico version of the Milky Way bar has a layer of caramel in addition to the nougat, and 3 Musketeers is essentially the global version of Milky Way. Our bars may be also bigger in size.
The Milky Way and the Mars bar were both created by the same person. And the Milky Way was created about 12 years earlier in Chicago. Forrest Mars went off to start his own Mars candy division in the UK after a fight with his dad.
I had a client that had a Mars heir as a client, and knew they were based in the DMV. I was curious how an American candy company with a candy bar named after the family ended up being created in the UK.