In terms of geological continents yes, but while some of the species in the North America pack do have ranges that extend into Central America, it's realistically a USA and Canada pack in terms of overall flavour. I feel like with things like Sloths, Armadillos, Howler Monkeys and Coati on the table still, there's a ton of space to get in some pretty distinct families.
I understand your point, but calling Mexico Central America is wrong in any sense of the word and it would be best not to fuel misconceptions that people may already have.
As for the NA Pack, it really does feel like a USA-Canada pack, despite having animals ranging further south (i.e. cougar, sea lion, beaver, prairie dog, bullfrog), as most of these are marginally Mexican (i.e. beaver, prairie dog, bullfrog) and only two have substantial ranges in Mexico (i.e. cougar, sea lion).
I guess the only way to counter the USA-Canada pack feel would have been to include an animal from Mexico that doesn't range further north. Apparently, even having a predominantly Mexican animal, the California sea lion, with
most of its breeding range in Mexico and the cougar which ranges all throughout the Americas isn't enough.