The point being that there is no need to buy a ticket in the US just because you live in the US. The country of sale can be anywhere in the world as long as you find a point of sale, and many (maybe most) Oneworld offices in 100+ countries around the world are happy to sell to you (even if they don't fly to that country!). For example AA had a ticket office in Sydney for decades despite having no flights to Australia, and was quite happy to ticket OWE originating in Australia at the Australia price even if you lived in the US (and did not tell you to contact your local AA office instead).