I believe in those countries where inspections are performed by contractors, the contractors essentially follow the rules established for the AP ("Authorized Party") program.
The AP guidance says:
FDA expects the APs' reports and any clarifying information requested by FDA to be provided in English. Any documents collected from the manufacturer may be in the operational or working language used in the manufacturer’s facility. However, the time necessary to translate the firm’s documents may delay FDA’s endorsement.
My understanding is that when the FDA conducts other-country inspections itself, it uses a similar procedure, i.e. the inspector prepares a report with analysis and recommendations, and sends that report to Washington where it is reviewed in detail and a determination made. If the supporting information for that report is not in English, I believe the translation work in done in the Washington office, where the foreign manufacturer has no control over translation accuracy.
My view would be that a manufacturer that for some reason needs especially quick FDA responses would be well served to make sure that everything the FDA needs is already in English and well translated; but, this is voluntary.