Quite the opposite, English has been the source of many such pressures, e.g. post Norman invasion, but it simply adapted in borg-like fashion to redefine what English was; retaining some of the previous language and moulding itself to fit in some of the new language.
Rather than rigidly fight against new influence, it took new words while retaining some of it's own. It does this constantly.
Even Chaucer's English is difficult to decipher for a modern English speaker, and that isn't even that old.
> Quite the opposite, English has been the source of many such pressures, e.g. post Norman invasion, but it simply adapted in borg-like fashion to redefine what English was
What you are describing is the standard process by which languages change. It's not accurate to equate this with the systematic elimination of a linguistic group through ethnic cleansing, something which English has never experienced.
Many languages have been wiped out by genocides, and wiping out a language is a common explicit tactic in ethnic cleansings.
English has never been the source of a serious campaign of this regard, though.