Actually, the US Secretary of State has, in the course of history, had more administrative type functions than we currently think of. While now we think of the SecState as purely a foreign minister, the US Secretary of State was at one time responsible for being the certifying official for constitutional amendments that had been ratified by the states, and, IIRC, had some kind of official duties over the Great Seal of the United States. (I’ll have to try to find a cite for that last thing, though.) Those types of duties help one understand that the US Secretary of States and the states’ Secretaries of State once had more similar functions than they do today.
States’ Secretaries of State (heheh) are also usually responsible for things like corporate registrations, state archives, and official state misscellany.
Until the 20th century, the US Secretary of State was the United States’ principal recordkeeper, with custody over almost all the Federal government’s official documents and records. Those functions have largely been transferred to the Administrator of General Services.
And of course the Secretary of State was originally responsible for issuing judicial commissions, which is why the bedrock case of American constitutional law is Marbury v. Madison: