I think you are missing some context here.
Firstly if the company is established in the union then they need to be compliant for all their users no matter where they are [1] (so US resident, EU resident, whatever are equally protected).
So the relevant section for this is:
"This Regulation applies to the processing of personal data of data subjects who are in the Union by a controller or processor not established in the Union, where the processing activities are related to:
the offering of goods or services, irrespective of whether a payment of the data subject is required, to such data subjects in the Union; or
the monitoring of their behaviour as far as their behaviour takes place within the Union."
So lets look at Amazon. They are a US company offering goods in the EU. So if you make a purchase from them as an EU resident (living in Germany) from amazon.de to your home address, then any personal data you give them as part of that purchase needs to be handled in a GDPR compliant way.
If you now go on holiday to the US and order something from Amazon.com to be delivered to your hotel, even though you are an EU resident, they do not need to handle that personal data in a GDPR compliant way. But just because you are now in the US doesn't mean the data they hold on you about your purchase on amazon.de is suddenly free from GDPR protections.
Or to put it another way. Imagine the law did mean EU resident. What does Amazon.com do? How do they ensure they process an order in the US to a US address in a GDPR compliant way for an EU resident? They can't without asking for additional data to establish each persons residency. Which GDPR doesn't allow.
[1] https://gdpr-info.eu/art-3-gdpr/