[kiiski]

I doubt ease of learning really has anything to do with the current popularity of English. As soon as the USA stops being the dominant power in the world, English will start losing ground as well.

edit: Looking at the EF English Proficiency Index[1], English doesn't seem quite as universal as it feels like in the Anglosphere anyway.

[1]: http://en.wikipedia.org/wiki/EF_English_Proficiency_Index