A thought, prior to the GAW, the southernmost point in the US was at the California/Mexico/Pacific tri-point. (the California/Mexico border is *not* exactly EW). What is it considered now?
A) Still that.
B) the southern edge of the formerly Confederate Arizona (including Otl Arizona/New Mexico/Mexico tripoint), which means no single southernmost point.
C) the US enclave in New Orleans
D) US Controlled Key West?
I'm guessing the answer is B, but not sure. (And yes, the line in B probably does wiggle, but that can be dealt with by the US and Mexico.