> tilt the uneven power dynamic between employer and employee towards the employee
With here
> unions seem to often go overboard with impractical demands and are more political than in Europe
Gives you Union Employee who grab the power from the actual owners of the company. The relation is now even worse: The Union leader have both power, and no skin in the game. At least the employers cared about the longevity of the company.
Unions don't solve the power dynamics. They just tilt it to a new side. Worse: They encourage the idea that force (strikes) can yield power/money; which is why countries with Unions degenerate.
Of course, someone here is going to get angry because of the "poor" employees and their work conditions.