The FAA will issue a foreign air carrier Ops Specs under FAR 129.
"CAT II/III Approach and Landing Minimums (Foreign Air Carrier). AC 120-29 (CAT II), AC 120-28, and this order establish the lowest approach and landing minimums that can be authorized, under any circumstances, for foreign air carrier CAT II/III operations in the United States. These minimums are equivalent to the minimums authorized for a comparably equipped U.S. operator. The CAT II operating minimums are specified in OpSpec C059 (H108 for rotorcraft), and CAT III operating minimums are specified in OpSpec C060 (H109 for rotorcraft), and in a manner similar to minimums specified for U.S. operators. The airborne equipment required for CAT II/III operations must also be specified in the appropriate OpSpec."
Then you have to dig through AC 120-28 and 120-29. The way I remember it (for my airline) is I need one RVR report (at touchdown) for a CAT I, two reports (touchdown and rollout) for a CAT II and three reports (touchdown, midfield and rollout) for a CAT III. With the note as Jammed Stab said that if the rollout is inop for a CAT II we can use the midfield and either the midfield or rollout can be temporary inop for a CAT III. Like a lot of stuff in US airline ops, it's whatever your FAA office approved. For foreign air carriers that's usually the JFK International Office.