>I have a recollection of being taught that immigrants to the US were forced
>to learn English in order to gain naturalisation, but maybe I'm wrong there.
I'm not sure of this but I do know that when I moved to Iowa, I discovered
that during the first world war, Iowa passed a law forbidding the use of
German in public schools (and there were a LOT of German communities in Iowa).
The French at one point DEFINED their language and required all citizens to
speak that language and only that language. It doesn't happen in just Wales or
the US. It happens everywhere.