Running a wire from an existing interior outlet to a new exterior outlet which is lower than the interior one
You will have to fish wire through... so you need a path. Professionals utilize a variety of specialty tools and special skills to do what you describe.

I would probably remove a KO and probe down the wall with a stiff wire to see if there was an obstruction. if there was, I would tear out the existing interior box, cut open the wall, use a long flexible drill bit to punch a hole, then patch it up.

You can spend a whole bunch of time fretting and trying to find an "easy way", or you can just do it and prepare yourself for the work involved patching it up.