And in those countries, iOS has a much smaller market share. You're proving my point.

The sum of all these smaller markets is still bigger than the US one.

When measured in terms of mouths, yes, but when measured in terms of surplus spending power than can go to Apple, certainly not.

India has 1.3 Billion people in terms of counting mouths, but not wallets with $1000 to send to Apple for a new iphone.

The biggest region in term of revenues for Apple revenues is all americas but it is still only around 43%, which means Apple still makes money from Africa, Europe, Asia and Ocenia combined than the whole american continent. So that is even less for the USA.

https://bullfincher.io/companies/apple/revenue-by-geography

You are doing a lot of heavy lifting lumping Europe and Asia together, and inserting Africa and Oceana, which is so small Apple doesn't even report revenue for it.

   North America is 43%
   Europe is 27%
   China 15%
   Japan 7%
   Rest of Asia: 8%
   Africa, middle east, oceania effective round to 0%

Basically North America and Japan make up 50% of Apple's revenue, but are nowhere near 50% of global GDP or population.

Nobody against the fact that US a is their biggest market. That doesn't change the fact that the more than half of their revenue is made in areas where imessage is totally irrelevant.