Unions are not the primary mechanism between employers and workers for establishing fairer wages in many European countries. Unions are designed to level a power imbalance between an employer (typically a legal vehicle which aggregates the material self interest of various actors) and the employees who would otherwise have to act alone.

Myopically focusing on wages while ignoring the many other concerns about the distribution of power and legal rights is a common misunderstanding.

Hourly wages in Germany are not that different from the US. Depends a bit on how exactly to compare - nominal, PPP, net/gross, etc.: e.g., average nominal is about 10% higher in the US, real median is higher in Germnay, ...