Pick an ad that travels
Some ads localize cleanly and some fight you all the way. The easy ones carry their message in captions and voiceover over product shots: you swap the words and the pictures still make sense. The hard ones have a presenter speaking on camera. The voice can be replaced, but lip movement is not always re-synced, and a mouth shaping English under a German voice looks wrong to anyone paying attention.
Before you localize, look at the visuals for things that belong to one country: a US-style kitchen, a dollar sign on a price tag in the scene, a Thanksgiving table, a car on the right-hand side of the road. None of them is wrong, but in a market where they look foreign they quietly tell the viewer the ad was not made for them.