I posted an article on the other forum about US diplomatic representatives. What I can offer right now:
George W. Erving, appointed from the state of Massachusetts. One of those to serve both in consular and in diplomatic positions. Served as:
Consul London 1801-1804; Secretary of Legation Madrid 1804-1810; Special Negotiator COpenhagen 1811-1812; Minister Plenipotentiary Madrid 1814-1819; Special Diplomatic Agent Madrid 1825.
BTW the record does not show any representatives being appointed to the Bonaparte court in Spain.
Robert A. Mosher