From what we could see from digging further, the US is the only nation in the world with a age of consent that isn't a single number. as such, it can be impractical to use. Correction, Australia has one region with 17 while the rest is 16. 

US appears to be primarily 16 (30 states + DC), with some states at 17 (8 states) and 18 (12 states). 
Taking that into account, we'd suggest going with the number that appears to be most common throughout the world (and throughout the US): 16.

But its not really as if we can truly verify the physical age of people in any case, so its a bit hard to do with 100% certainty.