The agreement will not be called a Treaty, because the Senate, particularly after the mid-term elections, will not pass it.
But it can still be imposed upon us by the heavily Left-leaning Supreme Court, which no longer makes any pretence at judicial impartiality and may well decide, even if Congress does not, that the Cancun agreement shall stand part of US law on the ground that it is customary international law.
B-A-L-O-N-E-Y!