That’s true, but there would be additional challenges. Outside of the US, Android dominates the markets to the tune of +80%. In order for such an effort to have teeth, there has to be incentive for them to comply. They could pull iOS out of the EU market and remove iMessage from macOS if it came down to it. They are already such a small percentage they might just eat the loss as the cost of protecting their walled garden. Unlikely, but a possibility nonetheless.