I am not so sure that american companies can just "hide" from this, they are actually quite exposed. Delta airlines, for example, appear to be quite worried by it internally, and are making changes to suit.
The scope of GDPR extends to entities providing services to individuals in the European Union so is not limited solely to citizens. Additionally, if an EU citizen is in the US and uses a US service provider's services, then that US service provider is not within the scope of the GDPR.
The legal disclaimer on the Verizon Up specifically states that the offer is only available to US residents.
On that basis I would say that Verizon, in relation to this specific programme, does not appear subject to the GDPR.
I don't know about the full extent of their services however so may be subject to GDPR if they satisfy the Art 3 GDPR requirements (https://gdpr-info.eu/art-3-gdpr/).
Certainly you realize there is a give and take here. The EU needs the businesses too. The EU is not powerful enough on it's own to just do whatever it wants. So they aren't going to go after these kinds of weird cases at first, because it would generate a large business backlash.