And LATAM will have no issue pulling the "standard" US-sized rollerbag if the gate agent deems it too large or weigh too much. Sometimes the gate agents will peruse the gate area looking for larger bags, and won't hesitate to pull and tag them. Although it has been a few years since I've been there, PMC was notoriously bad, especially at check-in, asking to see your hand luggage, and putting it on the scale. I once had to take my laptop out (and she gave me a plastic bag to put it in) because my bag was too heavy with it inside, although it was quite size compliant.

I can't say there's any rhyme or reason on enforcement, because I've seen some passengers with too many, and too large, bags boarding without issue, and others with what would be a compliant US-type bag hassled. When I travel short-haul on LA, I typically use a smaller carry-on bag.