Seems odd, surely you could argue it was because of British imperialism (which also brought English to the US)? The British empire once covered 1/3 of the globe, it seems far more likely a cause.
The British Empire dominated large parts of the world, but it never dominated continental Europe. English was not widely spoken or taught in Europe until the end of WW2, when American culture became highly influential (although the UK did have its part through pop music).
The final push for English came with the internet and thus again from the US, I think. In many European countries there is a big divide in terms of English proficiency between people who grew up in pre or post internet era.
If this were the reason, then English should already have been the lingua franca in 1900. But it wasn't.
But the previous spreading of the English language by the English Empire certainly helped when the US emerged as one of the main beneficiary of WW2.
Even at its peak, English language wasn't as widespread as now. The French language was, especially in 18th and 19th century, having substituted Latin.
After WW2, US absolutely dominated the world coming off as the only victor in WW2 (that's my personal opinion) and used their position to place English language as #1 language of the world (over time), undisputed. The end of the cold war cemented this even further.
We can argue that British imperialism helped somewhat, that I agree with.
I doubt it was intentional. Seems like it was a nice side-effect at most.
If that doesn't show intent, then I don't know what would :)
Don't get me wrong, I am actually impressed by it and gotta hand it to Reagan - winning a war without even firing a single shot.
Edit: I don't want to downplay the factor of oil and, but I feel like it's off topic here so that's why I don't mention it.
Hence the use of the Latin term “lingua franca”