A non-starter. The US company would have mandatory binding arbitration with a no class action clause in the contract noone pays attention to when they get the service. The arbitration details are secret. You would never know what others have attempted in the same argument against a similar US company. US company would, of course, know all the past attempts against them and know best how to argue.

As the arbiters may be blacklisted by the US company for ruling against them, they tend to bias to ones that favor the corporation against the human being.

In Corporate Ruled America, he'd have never received his "day in court". You do not get to use courts of law against a corporation in the US.

Could actually go pretty well, especially if picked up as a class action by a law firm expert in that area.

It is exactly the kind of systemic unfairness that the class actions are designed to handle -- too small individually to typically prosecute, but enormous in aggregate.

That said, legislation constraining class actions and terms requiring arbitration, etc. are setup as obstacles, and could be effective roadblocks. However since this was a deal before the contract with the fine print demanding arbitration, it might work (std IANAL caveat)

Possibly the same way. Both countries have the same common law traditions.

But I'm surprised that https://en.wikipedia.org/wiki/Statute_of_frauds did not come into play. This was a well-documented verbal contract, but still it was a verbal contract for 24 months. Which is more than a year, and therefore is more than a verbal contract should be able to cover.

I’m curious about american jurisprudence in this area.

In the US I generally have good luck with “pushing back” on corporations after having made verbal agreements with customer service, but not always.