The approval hurdle is high because the Constitution makes a ratified treaty the supreme law of the land — essentially, the equivalent of a congressional statute. The idea, then, is that no international compact should be imposed on the American people unless an overwhelming majority of elected officials in the upper chamber are convinced — to the point of willingness to cast an accountable vote for the proposition — that the compact serves the national interests of the United States.
Not of the world. Not of the Earth. Not along the lines of harming ourselves in order to set an example for China and India that will purportedly be a boon to humanity and the planet. An international agreement must plainly benefit the American people. If it does not, the treaty clause’s operation will reject it.
Transnational progressives believe this is a bug. To the contrary, it is the feature.
Note that the Constitution does not merely presume against foreign entanglements. It consistently elevates the national interest over both foreign interests and global interests — if there be such a thing as the latter. (That a bien pensant transnational progressive tells himself the earth is a communal asset to be curated for the common good hardly means that’s how they see it in Beijing . . . or Moscow . . . or, for that matter, Appalachia.)