> I think many of the factors which can make public sector entities less efficient - e.g. harder to get rid of underperforming employees, fewer institutional rewards for reducing unnecessary expenditures - apply broadly across countries

It's much easier to remove a Federal Employee in the US compared to Germany. The "give 3 documents" rule makes it easy to not have to deal with lengthy arbitration. At worst, it's comparable to private sector hiring/firing rules in Germany.

Furthemore, hiring practices for federal jobs are much more decentralized in the US compared to Germany.

And finally, the entire corpora of statutes, legislation, and administrative policies in the US is significantly different from that in Germany, such that any surface level similarities are basically convergent evolution.