* Governments can reach Apple and Google, and thus force them to remove the apps from their app stores.
* Diplomacy. EU and USA will have a lot of negotiation to do pretty soon. USA doesn't like how EU handles big tech and privacy. EU doesn't like how USA's preferred treatment of domestic electric cars in the "inflation reduction" act that went into effect a few days ago. If Meta pulls out of EU to dodge enforcement, the EU diplomats will surely bring that up, and work a solution into whatever treaty comes out of this.
2. Lowest effort DNS blocker to exclude the 90% who don't care enough to circumvent.
2. Let the lack of network effects and time do the rest.
Sure, a few will hold on, and there will probably be a temporary "buy a phone with fb installed for 10000$" market, but given time, Facebook/Whatsapp/etc. will be dead in Europe.
Correct, however most countries have various related criminal offences. (e.g https://www.legislation.gov.uk/ukpga/2018/12/section/170/ena...) It's extremely unlikely any of these would be relevant in this context though.
