>The argument for most people is that rights are universal
No, they are not. Clearly the US and Germany do not have the same rights. They also have changed over time and will change in the future, as the labor market changes.
>and it is fair, just, and essential for workers to have life, liberty, and the pursuit of happiness, etc.
But these are not the rights a worker in Germany has. Worker rights in Germany derive from the belief that the employer has a duty to care for his employees, which also does include limiting the freedom of their workers, if necessary. E.g. you are forced to pay health insurance as an employee.
Additionally social stability is good for everyone, especially the workers.
The rights are fundamentally the same: safety, reasonable treatment, wages, etc. The interpretation differs.
Germany does subscribe to fundamental, universal human rights, and worker's rights are partially derived from it. Universal human rights are at the heart of German and US politics, morality, philosophy, and anything else.