I would like to make some corrections: Why is English so commonly compared to other languages?

I agree with Peachey. If you look back even further, to the Roman and Greek empires for example, we can see that the language of the invading nation became the "lingua franca" (common language) of all the peoples subject to the invading nation. As for the USA, I heard that, in the early days of the American nation, there was a debate on which official language to choose - English or German. English was chosen by a narrow majority.

A quick look at the last few hundred years of history shows that the more widely-spoken languages originally belonged to those countries which actively invaded, colonised and took over other countries.

This is a fascinating question. I think there's a common answer and an uncommon answer. The common answer starts with the industrial revolution, which itself started in England, making that nation into the largest empire the world had ever seen (controlling about 25% of earth's land mass) and bequething their language as well as scientific, academic and legal influences around the world. Of course the U.S. (which could be argued is also an empire) expanded in all these areas, especually culturally (through movies, music, etc.) and economically. But here's my uncommon answer: English is an incredibly dynamic language, an amalgam of linguistic influences that go back over a millennium. Think about the English lexicon. 80-85% of words come from greek and latin. (Showing the influence of those empires). Some of the basic subject and personal pronouns (like they and there) and other words (like know and knife and sky) are viking. And of course, there are influences from French as well, although the grammar is germanic to its core. So, while English may be the lingua franca right now, it's worth while to remember that the English language is a living pathwork of linguistic influences.

I would say that also the excellent level of several American and British Universities (sorry, I don't know about Australia or Canada) and the enormous scientific production wtritten in English give a sound foundation to the spread of the English language in such proportion. About Australia and Canada: I like to cite the great songs in the English language of: Nick Cave Leonard Cohen How many perople fall in liove with English just listening to them? I would say quite a lot.