Apple reported 30bn net sales in Europe in the last quarter: the second biggest region after the US. Although some of that'll be driven by non iOS stuff, we know that's the main earnings driver.

In a future where Apple have withdrawn the app store, who in the EU is going to buy an iOS device?

Sorry, but the idea that they'd be able to justify pulling out to shareholders over this is pure fantasy.

edit: source - https://www.apple.com/newsroom/pdfs/fy2024-q1/FY24_Q1_Consol...

Apple has shown with China that they're perfectly okay with localized rules in their systems. If you think they wouldn't make a few EU-only changes to preserve a whopping 7% of the revenue I don't know what to tell you. 7% is much more than you make it seem, and actually as someone else pointed out the real number is higher because without App Store the iPhones are worthless.