If Facebook certifies deletion of certain data, and somebody doesn't believe them, they can sue in an American court. If WeChat certifies deletion of certain data, and somebody doesn't believe them, they're SOL.

Why are most companies (i.e. USAToday complying) when they have no market, interest, or presence in the EU?

Ha! Good luck getting a single euro out of China! We've already seen the EU roll over when Russia's energy giant Gazprom applied a little pressure.