In South America and Europe, it's less than 20%, which is as low as that map goes. The only really high Chistian area where it's also common is Africa.

It's true that there's overlap between places with Christianity and places where circumcision is encouraged, but you're making it sound like it's encouraged as part of Christianity, which it's not. Or that Christian nations in general tend to be more in favor of circumcision, which they do not. Otherwise why would you end up with all those extremely Christian countries like Mexico having very little circumcision?