To determine what constitutes the United States for purposes of §168(g)(1)(A), you'd need to look to Treas. Reg. §1.168(i)-4(d)(2)(ii), which deals with when a property is deemed to have been used predominantly outside the United States.  Since the determination is made by reference to §1.48-1)g)(1)(i), we'd then need to look to that reg. for the details.

§1.48-1)g)(1)(i), in turn, refers to §7701(a)(9) for the definition of the United States and that code section states clearly that "[t]he term “United States” when used in a geographical sense includes only the States and the District of Columbia."

This means USVI and Puerto Rico are not considered part of the United States for purposes of §168(g)(1)(A) and ADS will be applicable when tangible properties are used predominantly in those locations unless one or more of the exceptions under subparagraph (g)(4) are met.

[You will notice, however, this is in contrast with subparagraph (6)(B), which specifically includes Puerto and US possessions within the definition of the United States for purposes of that particular subparagraph.]