Hi Marc,

One small point on the following from your post:

... it has everything to do with the US government keeping its pledged word to the international community.
That "pledged word" is always subject to the US Constitution, as reflected in Reid v. Covert and other cases. Sometimes, that is stated in an express reservation to the treaty; but, it is always implicit if not expressed:

http://en.wikipedia.org/wiki/Reid_v._Covert

Reid v. Covert, 354 U.S. 1 (1957), is a landmark case in which the United States Supreme Court ruled that the Constitution supersedes international treaties ratified by the United States Senate. According to the decision, "this Court has regularly and uniformly recognized the supremacy of the Constitution over a treaty," although the case itself was with regard to an executive agreement and the [sic, "a"] treaty has never been ruled unconstitutional.

The case involved Mrs. Covert, who had been convicted by a military tribunal of murdering her husband. At the time of Mrs. Covert's alleged offense, an executive agreement was in effect between the United States and United Kingdom which permitted United States' military courts to exercise exclusive jurisdiction over offenses committed in Great Britain by American servicemen or their dependents. The Court found that "no agreement with a foreign nation can confer power on the Congress, or on any other branch of Government, which is free from the restraints of the Constitution." The Court's core holding of the case is that civilian wives of soldiers may not be tried under military jurisdiction, because the Fifth Amendment's grant for military jurisdiction, i.e. "except in cases arising in the land and naval forces" cannot sweep in the jury-trial requirement reflected in the Fifth and Sixth Amendments.
Links to opinions in Reid v. Covert are at:

http://en.wikisource.org/wiki/Reid_v._Covert

Executive agreements (whether congressional-presidential or presidential only) and treaties are subject to the same limitations - and can validly cover the same subject matter. I wrote on that topic 40 years ago (my only academic publication ).

Constitutional Law: Executive Agreements: International Law: Executive Authority concerning the Future Political Status of the Trust Territory of the Pacific Islands. Michigan Law Review, Vol. 66, No. 6 (Apr., 1968), pp. 1277-1292 (article consists of 16 pages) Published by: The Michigan Law Review Association.
GC's (especially common Art. 3) are more of a quagmire. Still struggling with those in light of the recent cases, without reaching any firm conclusions.