How many decades?
I knew some British guys in the early-mid 90s who were horrified that teachers in their department were still using some version of RP/Queen's English as a model for their students.
I was told that that accent would make them instant targets of dislike in the UK (they put it a bit more colorfully). After some effort, they managed to get something a bit more realistic put in place.
The basic problem is that there's no neutral version of British English, it's all highly marked for region or social class (and sometimes other stuff).
The US does have a standard that's neutral for class and region and ethnic background (General American English). Some people move between it and something more defined as the occasion demands.