That is only historic influence, though. Britain does not control the English language and cannot exert any further influence through it.

It has profound foundational influence that continues to this day.

Also, England doesn't need to do anything to ensure that influence of English culture is maintained in the US either.

For as long as we still speak the English language, English culture will continue to live "rent free" in our heads, and that's not going away anytime soon.

This is often cited as a "soft power".

Well, Monthy Python does still reach some people, but apart from that it is fading away it seems ..

The lingua franca has changed before...

Yeah, but whose English?

I think you meant,

"but whom's English"