The text of the Rome Statute is clear. Article 98(2) is unspecific as to the variety of international agreements that it covers, unlike the narrower Article 98(1) covering diplomatic immunity.  Article 98 Agreements are a tool that is a legitimate method of the US ensuring that US citizens are not subject to trial and punishment by a court which the United States is not a part of. This would run against the principle that a treaty only affects states that have signed and ratified it, rather than any others.