young!America starts to understand what it means to be a colony- when he meets Mexico and Brazil for the first time.
I kinda headcanon America as being quite a precocious and intelligent child, who grew up really fast. So, the thing is seeing how things were in Brazil and Mexico where industries were a lot more extractive and things were more authoritarian, he started to realise how although England treated him well, in some ways, England saw him as a mine of riches that would further enrich the empire. Not quite a “family” or “brother” the same way humans would.
(Also, I really just wanted to draw more new world babies!) Btw, I imagine young!Mexico and Brazil would have known each other quite well even if they were separately controlled by Spain and Portugal, because of the Iberian Union- and Brazil’s the tallest here because he’s the oldest of the three of them. The latin americans are my own design, but inspired by the latin hetalia community.