I believe he does have a cop-out if HN isn't selling to or marketed towards the EU, but I thank you for sharing your experience because I'm looking to shut my account in the near future.
Nope, GDPR attaches regardless of whether you market in the EU/to EU residents, as long as you provide goods or services to people in the EU you're beholden to their rules.
Theoretically, a company that only offers services to US residents (mortgage/banking/legal) could still be beholden to GDPR, since their cardholders might access their website (i.e. be provided services) while in Europe, though as far as I know it's never been tested in court.
The EU has full jurisdiction within the EU, and zero without. The EU has no ability to demand action or inaction from an entity in the United States. They can ask all they want but it's just that - a request.