Q&A: Mahan already had the War of 1812 warning

Could Prussia's naval failure have warned Mahan against an understrength United States fleet?

Yes, although the War of 1812 already showed that American naval quality could not offset a much larger British concentration indefinitely.

Prussia's improvised navy could have warned Mahan against relying on an understrength fleet, though the War of 1812 offered a more direct American example. The United States Navy performed well while it faced forces on a comparable scale. Once Britain deployed a much stronger concentration, that local freedom quickly disappeared. The answer separates tactical quality from the strategic limit imposed by fleet size.