If the President of the United States is the "leader of the free world", then why don't the constituents of the free world get a vote?

In a nation where the electoral system is a veritable dog's breakfast, the election of a POTUS is the result of a mish-mash of (to mix animal metaphors) "first-past-the-post" systems. Which means that, unlike Australia, you can't allocate votes for your local POTUS Electoral Collegians on a preferential basis. It's all or nothing for the candidate of your choice.