As the Prez has said, there are decisions being made that affect the US so it is wise to have a seat at the table.
Without a seat, the US has no way of presenting the data, and as those maps show, it is significant data.
Without a seat, the US has no way of making a claim.
With a seat, the US has no way of recovering on a claim. Not in a third world/UN forum. Not a chance.
Besides, there is always that "gunboat diplomacy" to which you were in thrall a few posts back. Ready to give up on that so soon? Far better, no UN taxes and no submitting to an international court--bottom line = no diminution of our national sovereignty. While this is unimportant to you, it is a critical issue for loyal Americans.