Uhhh - someone didn't check their facts here. I remember when the .280 Remington's designation changed to be "7mm Remington Express", and that certainly wasn't in 1957. Yes, the .280 came out in 1957, but the nomenclature wasn't changed to "7mm Remington Express" until 1979. My copy of Hodgdon No. 26 says:

"...In 1979, in an attempt to revive their dying cartridge (the .280), Remington changed its name to 7mm Express Remington."

Volumes could be written about Wikipedia's errors....

Now, by the late 1970s, another metric cartridge - the 7mm Remington Magnum - was very firmly extablished as a "favorite" in many AMERICAN hunters' arsenals. So, you get Maggie's Drawers for the suggestion about WWII and metric calibers in the context of and the reason for the 7mm Express's low popularity. If that were true, the 7mm Remington Magnum would have suffered the same fate.