Actually, that is incorrect.
The British had designed a bullpup style rifle in a new mid-range .280 (7mm) cartridge in 1951, no less. The rifle/round were accepted by the British army, but was cancelled by Churchill in favour of NATO standardization, with the 7mm cartridge in the competition.
The idiot American in charge of choosing a new US cartridge insisted the 7mm was insufficient and not powerful enough.............and only a full power .30 (as in the 7.62 x 51) would be accepted by the Americans. As standardization was dependent on accepting the same cartridge as the USA.........NATO followed suit, despite very good reviews on the 7mm.
https://en.wikipedia.org/wiki/EM-2_rifle
Ten years later the USA went to 5.56, a much less powerful round than the Brit 7mm. A missed opportunity.
The 7.62 x 51 is entirely an American invention, and was adopted solely on their insistance.
You are ignoring history.