It does, if the company has any branch/office/agent or similar in the EU, or if it targets their services/website to EU residents.
What "targets" means exactly in this case I'm not sure, but given that YC actively markets to EU based companies too, I would think that GDPR applies to them as well.
What "targets" means exactly in this case I'm not sure, but given that YC actively markets to EU based companies too, I would think that GDPR applies to them as well.