Ask HN: Will GDPR help non-EU citizens?

Folks, there are a few gray area type of questions about GDPR that I do not understand:

Will it be helpful at all for non-EU citizens? Only if the used service is european perhaps?

What about US companies providing services to europeans? Does it really apply to them? Could I be subject to GDPR if using a service via an EU-based VPN?

Is GRPR really mandatory immediately after May 25th? I didn't see big internet companies talking about it, won't they just ignore it until someone goes to court?