Android is more dominant across the world, and it turns out that it's just open enough that even more open platforms like mobile Linux have not retained comparable developer mindshare.
In the US however as a result of differing strategy behind text and data costs by telecom providers in the 2000s Apple were lucky that it disincentivised using data for messages, so there wasn't the same internet-based messaging app uptake that took place elsewhere globally and basic SMS remained dominant.
Then when iMessage launched in 2011 telecom providers plans had changed enough so that data wasn't as expensive, so it became seamless to keep using the default iPhone messaging app to talk to everyone.
In the US however as a result of differing strategy behind text and data costs by telecom providers in the 2000s Apple were lucky that it disincentivised using data for messages, so there wasn't the same internet-based messaging app uptake that took place elsewhere globally and basic SMS remained dominant.
Then when iMessage launched in 2011 telecom providers plans had changed enough so that data wasn't as expensive, so it became seamless to keep using the default iPhone messaging app to talk to everyone.