> The US signature was shaky to begin with (it was never really ratified through the proper channels) and I doubt they would've kept their signatures with the impending invasions following 9/11.

What you are saying here is a bit confused. Under US domestic law, the President has the unilateral authority to sign whatever treaties the President wishes. Ratification comes after signature, the US never ratified the Statute. So there was nothing actually "shaky" about the signature.

This is a topic which confuses a lot of people. Agreeing treaties under international law is a two-stage process – the first stage, "signature" is in-principle agreement but isn't actually legally binding (except for a limited obligation "not to defeat the object and purpose of the treaty", and it isn't very clear what that even means); "ratification" (sometimes also called "acceptance" or "approval") is fully binding agreement. For less important treaties, the two stages are sometimes collapsed into one ("signature without reservation as to ratification"), but for major treaties the distinction is generally preserved. Also, joining a multilateral treaty subsequent to its entry into force is often a single stage process ("accession"). However, the average person doesn't understand this two-stage process, and is used to everyday contexts where signing a contract is sufficient to make it legally binding.

There are some particular reasons why Americans find this even more confusing than people of most countries do. Many Americans have the idea that the US Constitution requires treaties to be ratified by a two-thirds majority of the US Senate. However, strictly speaking, the President ratifies treaties, not the Senate; the Senate just gives the President permission to do so. Furthermore, US law distinguishes between "treaties" (whose ratification requires two-thirds Senate consent) and "international agreements" (whose ratification doesn't) – but as far as international law is concerned, both are treaties – whether some act of ratification requires consent by the US Senate is an internal American matter with which international law is largely unconcerned.

Actually, US law distinguishes three types of "international agreements" (all of which are treaties as far as international law is concerned) – treaties (President ratifies with consent of two-thirds of Senate), congressional-executive agreements (President ratifies with consent of ordinary majority of both House and Senate), and sole executive agreements (President ratifies unilaterally). It is generally understood that "treaties" are used for foundational legal issues, military alliances, borders, human rights, etc; congressional-executive agreements are primarily used for trade; sole executive agreements are used for more minor matters of international cooperation. However, there is no precise legal rule regarding what type of agreement is to be used for which category–the Supreme Court views it as a "political question" which it expects the President and Congress to sort out between themselves, largely without its input. Under international law (Vienna Convention on the Law of Treaties article 47), if the President ratifies something, that ratification is still binding under international law on the US, even if US Congress (or even the Supreme Court!) decides the ratification to be illegal or unconstitutional – unless its illegality/unconstitutionality was "manifest" and "objectively evident" to the other states parties at the time the President made it.