We're talking about web browsers. Pretty much everyone with a personal computer(including smartphones) needs one. The US makes no sense as a subset here. If we were discussing what markets for a company to target, then sure. But we're not, are we?
I and many people here abandoned Chrome, so it’s only relevant to me from a software development perspective.
In terms of software development a US specific audience isn’t uncommon. Local utilities and many government agencies etc just don’t care about foreign users.
> Unless you’re equally interested in non English speaking users then the global average is absolutely meaningless.
The US is not even the largest English speaking population, it’s India. Additionally, if a subset is to be chosen, why is this subset from the US? Why does it get to be the centre of the universe, especially for a general-use product like a web browser?
The point was it’s rare to care about global numbers, not that the US is the only meaningful subset.
As to why a US only subset may be reasonable vs a language specific subset, some US government agencies care about a global audience but many are US specific. They may have multiple languages because Americans aren’t all fluent in English.
Unless you’re equally interested in non English speaking users then the global average is absolutely meaningless.
What matters to organizations is some subset of everyone and what their specific access looks like.