> See: the way "favours" are portrayed in The Godfather movies, for an image of the American mindset on what owing someone a favour / being in someone's debt is like.

Maybe not that extreme, but yeah, it's too easy to get guilted into something because you've become socially indebted by something large.

It's not even about being able to get out of it, like you mention afterwards with a legal exchange, it's about the exchange being forced to continue out of a mixture of guilt, politeness, and social pressure in general, simply because you don't want to accidentally kill the personal relationship.