Something worth noting that a lot of comments are ignoring here: while this fine is coming from the EU, these kinds of data protection rules are _everywhere_ now - this is no longer really EU-specific.
The reality is that it's not an US companies vs EU data protection law battle - it's US companies vs data protection laws in the comfortable majority of all other developed nations. The EU, UK, Switzerland, Canada, Brazil, Israel, South Korea, Argentina, Japan, New Zealand, Indonesia, Uraguay, etc, all have substantial data protection legislation. The EU has an published list of countries whose data protection laws are considered equivalent to GDPR: https://ec.europa.eu/info/law/law-topic/data-protection/inte...
While it's the EU fining Discord in this case, presumably the equivalent laws in each of those countries would also come to similar conclusions everywhere else too (though so far it seems the EU has more political appetite and clout to press the issue).
There's no world where Discord or other major US companies can pull out of the EU and keep following these practices, even if that was worthwhile. To avoid having to implement data protection practices, they'd have to drop the vast majority of all international users (and in Discord's case, https://www.similarweb.com/website/discordapp.com/#traffic suggests the US is currently <30% of their user base, so that's just not happening).