If you extend the conversation, I think that we could infer that none of the currently "popular" metric cartridges would have much traction in the U.S. except for the infusion of cheap surplus military rifles post-WW1 and again post-WW2. The 6.5x55 would be a niche cartridge without all the surplus Swedish Mausers imported since the 1950s. The 7x57 would be the same if not for all of the surplus Centeral/South American Mausers, both small and large ring configurations. The 8x57 would also be the same if not for all of the war trophies and surplus German 88s and 98s.
I do believe that would be the case.
