IEC cables sizes area in sq.mm. or mm^2. NEC , Chapter 9 , Table 8 has areas of AWG conductors in mm^2.
As for arc flash labels for MCCs, depends on local codes, but if you are in the NEC world, the answer is Yes. There is no distinction or exception for IEC or ANSI type equipment in NFPA 70E.
I agree with Rafik about arc flash test. The new IEC 62271-200 requires an internal arc testing of substation with installed switchgear, but the classification is only valid in combination of the switchgear used for the test. See:
section 8.3 Internal arc classification
I think NEC gives the circular inches for an AWG conductor symbol and as 1mcm=0.5067 sqr.mm you can calculate the equivalent sqr.mm.
Never-the-less NEC "translated" the AWG into metric system, as the IEC cable conductor crossection follows IEC 228, so one has to fit the "AWG" crossesction accordingly.
For instance 4/0 AWG is 107.2 sqr.mm. That means you have to choose if it will be 120 sqr.mm or 95 sqr.mm.
