U.S. unilaterally claims control of Papahanaumokuakea maritime area

First off, the United States is not a member of the UNCLOS, the United Nations Convention on the Law of the Seas, that has been ratified by over 150 nations and generally regarded as the governing body in connection with international maritime affairs and consultation. So how is the U.S. able to unilaterally declare its control of such a large body of waters and islets(and with it, resource and mineral rights) within such a huge swath of heretofore unclaimed territory?

Secondly, it is precisely the U.S. that has recently and actively pushed the Philippine government to pursue a one-sided Arbitration against China(which is a UNCLOS signatory and has the right, within UNCLOS provisions, to abstain from such arbitration), regarding some South China Sea islets. Meanwhile, the U.S. aggressively sent nuclear armed gunboats to within 12 miles of China's claimed South Seas territories to challenge Beijing, and specifically condemned China for unilaterally declalring ownership of those territories. Isn't there a heavy dose of hypocrisy on the part of the USA government in grabbing the Papahanaumokuakea region?

Finally, there has been some "below-the-horizon" mention that indeed the US Navy is going to locate--as in the North Atlantic waters--an entire network of underwater sonars, to monitor potential submarines in the area. What is the geo-political fall-out from such militarization of this previously pristine area?