According to some stats I have found[1][2] it does not seems like there is any exodus, if anything it seems that iOS gains market share every December (gifts?) and then loses a bit over the year, but the number has been stable since forever.
There are definitely less iPhones in Europe than in US, but that is more of a reflection of the global trend. iPhone was dominant in US because for a long time they had a carrier subsidy system that made it not worth it to buy a phone on a plan for less than $450 (because you paid the same price no matter the price of the phone). Back at that time that's what an iPhone cost.
In Europe the subsidies worked differently so the price was a more important factor.
There are definitely less iPhones in Europe than in US, but that is more of a reflection of the global trend. iPhone was dominant in US because for a long time they had a carrier subsidy system that made it not worth it to buy a phone on a plan for less than $450 (because you paid the same price no matter the price of the phone). Back at that time that's what an iPhone cost.
In Europe the subsidies worked differently so the price was a more important factor.
[1]: https://www.statista.com/statistics/461900/android-vs-ios-ma... [2]: https://deviceatlas.com/blog/android-v-ios-market-share#germ...