Being from the UK it may sound strange to US and other international folk that it sounds very odd when someone says they are 'anything' - American, as in Cuban-American, Iranian-American etc.
Outside the new-world migrants aren't routinely (or ever) labelled with their ethnic history and their citizenship details. I would be an 'Irish-Britain' in that were the case and I've never heard of a 'French-German', for example.
If you are a citizen of a country then that is what you are, in both cases related to Apple, the customers are simply American and that is all there is too it and should have been the end to the problem and their ethnic origin should never have been called into question.
When it comes to matters of cultural identity then it is clearly of importance but as this issue specifically relates to Apple's unwillingness to sell goods to citizens of countries it doesn't agree with the customer should just use simply explain they are American and insist that their grievance be taken up by a higher-power (or else!), plain and simple.
Rather than see the incidents as a racial matter turn the argument around and make it one of consumerism and hit Apple where it hurts. The customer could potentially sue Apple or take the issue up with the feds as according to the Federal Civil Rights Act;
people are guaranteed the right to "full and equal enjoyment of the goods, services, facilities, privileges, advantages, and accommodations of any place of public accommodation, without discrimination or segregation on the ground of race, color, religion, or national origin."
Surely Apple are therefore breaking Federal Law by refusing to sell on grounds of racial bias which would quash\trump any claim to the 'right of first refusal' that any retailer could argue was theirs to employ?