IMC007
If you have already done the ATPL studies then you have completed 99% of the syllabus of the ICAO flight ops officer/flight (not ramp) dispatchers licence. You would be able to complete the FAA Dispatchers licence with relative ease, US weather, FAR'S and the US AIM probable the only study required.
Although, you lack direct ops office expereince, this would come on the job in time. I would apply for any ops officer vacancies citing your fATPL. You might find some companies are concerned about taking fATPL's worried that they will skip at the first flying job that comes along. Have an answer to that question.