It's the same in Germany and France I think, but then you have Denmark where iMessage is like huge. The point is that the EU isn't particularly homogeneous in terms of messaging platforms. The only thing that is true across the EU is that Facebook/Meta is in control of most of messaging.
In the US, the regular message app (which is to say, the one you’d use to send an sms) automatically goes through iMessage if you send from one iPhone to another. The bubble turns blue, but I think most people just think of it as “a text,” generically, other than weirdos who are too into messaging protocols.