The root cause of every social problem in America (and most other places) is patriarchy - a male led dominance based hierarchy that is maintained and upheld by coercion, intimidation, and violence. bell hooks noted that it was integrally tied in with predatory capitalism and white supremacy because all are systems of hierarchy and oppression. All places that practice patriarchy teach that males are more important and "better" than women - it's not unique to America - it's the way that the system justifies itself and the hierarchies with in. But, as already made clear, because it's a dominance-based hierarchy, patriarchy harms men too.
The APA summary I linked you was just that, a summary. Google APA men and boys guidelines to find the entire 21 page report.
