Well, only Americans use it. There's no point in arguing about it your version of a language is better or worse but for the rest of the world it's incredibly annoying having to correct Zs with Ss when using LLMs or American only software.
I could cite many sources but https://en.wikipedia.org/wiki/American_and_British_English_s... provides a simple view.
But when you look at things like the type of English being taught in school, or the language used by the government, it'll be UK/International English.
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.
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...