What evidence is there that no culture had even a notion of an individual prior to some date? The notion that individual persons have specific obligations, responsibilities, and entitlements based on their position within a social structure is common in cultures that predate contact with the West.

More to the thesis of your post, the idea that the notion of the individual is somehow singly responsible for negative social consequences is contradictory when those consequences are considered negative because of their impact on individuals. Homelessness, poverty, discrimination, etc - these are bad because they are things that degrade the experience of individuals in some regard. If they didn't negatively affect individuals, then they wouldn't be negative consequences, and you likely wouldn't care as much about them.