There is absolutely nothing stopping an American, Japanese, Iraqi, Venezuelan, Russian, Chinese, German, or Indonesian company in offering its products for sale to foreign customers in Canadian dollars, yen, renminbi, dinars, rubles, Euros, or bhats. A US carrier isn't going to appear off the shores of your country for doing so.
They don't do so (or, when they do so, they also denominate in US dollars) because customers by and large prefer using US dollars. They also like using Euros, yen, and Swiss francs. (They have no problem with Canadian or Australian dollars, but obtaining it can sometimes be more difficult.) But the US dollar is the one currency that is absolutely, positively, 100% guaranteed to be wanted by both the buyer and seller, no matter where and for what.
Let me repeat: The primacy of the US dollar is driven by demand, not supply.
They don't do so (or, when they do so, they also denominate in US dollars) because customers by and large prefer using US dollars. They also like using Euros, yen, and Swiss francs. (They have no problem with Canadian or Australian dollars, but obtaining it can sometimes be more difficult.) But the US dollar is the one currency that is absolutely, positively, 100% guaranteed to be wanted by both the buyer and seller, no matter where and for what.
Let me repeat: The primacy of the US dollar is driven by demand, not supply.