Non-US corporations, of any size, have no duties towards US residents whatsoever. It's entirely their choice whether or not to enter foreign markets. Americans are not default humans, and they do not decide what products other nations' companies offer them.
Not a duty to the people buying, a duty to the owners of the company. To make a profit out of easy opportunities. Or justify not doing it, to the owners.
And the duty to owners is what you said yourself in your other comment, so I'm not sure why you seem to not understand what I'm saying.
You are making the exact blinkered US-centric assumptions I'm poking fun at. US companies may be duty bound to put increasing owner value above other considerations, but fortunately out here in most of the world, your law does not apply to us, and our laws are not modelled on yours.
I can assure you, for example, that in many nations companies can legally have many reasons for choosing not to export a product to a specific country that don't make any reference to profit. Again: all you know is your laws. Your laws are not our laws. It's a big world out here, not encompassed by the mores of the nation you just happen to come from.
Small entities can do whatever they want but big corporations should have justifications for not selling a thing.