I think belonging to a church probably helps a lot too, just because I know quite a few Christians from foreign countries and all of them have pretty mild accen

I think belonging to a church probably helps a lot too, just because I know quite a few Christians from foreign countries and all of them have pretty mild accents. Even the ones who've only been speaking English for a few years. Language immersion would be the obvious factor there but I have a hunch that group singing plays a big role too.