What percentage of US ambassadors and their US staff speak the native language of the host country?

Answer 1

The prior answer is someone's guess, and is wrong.

All diplomatic staff that comes into professional contact with members of the host government are usually taught the host country's language. The only exceptions are for employees who work only inside the Embassy and have no outside contacts: for example, communicators, budget officers, and the like. Sometimes a language waiver will be granted for a particular job that is otherwise hard to fill.

Some politically-appointed ambassadors are not expected to speak the language, but they are generally appointed either to countries where English is commonly spoken, or where they have excellent assistants with top language skills.

Answer 2

they don't necessary have to speak it but all of them have to understand it.