“The United States” means any territory under sovereignty of the U.S. federal government.
Ripple, Judge on the Seventh Circuit Court of Appeals '7[Kenneth F. Ripple;1-16-2007; Federal Judge on the Seventh Circuit Court of Appeals; "Arnett v. C.I.R, 473 F.3d 790," https://casetext.com/case/arnett-v-cir//JJB]
Indeed, with respect to the word "includes," the definition of "foreign country" largely mirrors the rule's definition of "United States" in its usage of "includes." See 26 C.F.R. § 1.911-2(g). The rule defines the "United States" as:
United States. The term "United States" when used in a geographical sense includes any territory under the sovereignty of the United States. It includes the states, the District of Columbia, the possessions and territories of the United States, the territorial waters of the United States, the air space over the United States, and the seabed and subsoil of those submarine areas which are adjacent to the territorial waters of the United States and over which the United States has exclusive rights, in accordance with international law, with respect to the exploration and exploitation of natural resources.