I regularly correspond to people from all over the world, India, China, Brazil, France, and they all tend to use US English, thus the suggestion.

Commonwealth countries are relatively minor in population compared to the USA and the rest of the world.

And yes, default US spelling in devices does play a role. See prev. point about technological and cultural dominance.

> Commonwealth countries are relatively minor in population compared to the USA and the rest of the world.

Given India's presence in the Commonwealth, this seems an odd assertion. 2.6 billion people live in the Commonwealth[1].

[1] https://en.wikipedia.org/wiki/Member_states_of_the_Commonwea...