Why would the US be party to a treaty that constrains mainly the US? Whether the restrictions on deep sea development or deep space, the US is so far ahead in technology that the treaties serve only to give the vast group of second-placers a chance to catch up. As if they actually have the ability and desire to catch up.
It's not catching up they have in mind. It's reining back the lead horse--America.
They don't care if they live in mud huts...as long as we all do, unless we're UN diplomats, of course.