The German government is legally obliged to ensure the human rights to social security and to an adequate standard of living contained in international treaties it has promised to uphold. Related treaties, standards, and guidance on social security, from UN and European human rights bodies, set out requirements for social security benefits to be adequate.
Germany’s Constitutional Court has developed jurisprudence on the minimum subsistence level required to live in dignity. This requires the state to ensure that people are left with at least enough of their earnings to cover their necessary living expenses, and to guarantee a minimum level of participation in social, cultural, and political life.
And here we see the gulf between legal requirements and implementation even in still-functioning democracies. It's still surreal that Germany is holding but the U.S. has failed.