Not exactly. I place it on the outside of the window. I have always understood that the decal must be permanently affixed, which I would think would rule out taping it to the inside, but each U.S. customs office is a litle different in their adherence to the rules.
When I asked a very similar question of the office at Ft. Pierce (FPR) Florida, they said that as long as it was visible when approaching the pilot’s side of the aircraft they were OK. I took that to mean that if it was on the edge of the door or door jam so it could be seen with the door open that was fine. Even the inside of the door would be OK.
For the record, most corporate jets place the decals on the airstair door on the vertical part of the step when the door is in the open (down) position.
Even so, I placed mine on the lower forward corner of the rear window on the pilot’s side. As for looks, I wear it as a merit bdge of sorts. All-in-all, not that many GA pilots fly internationally. The decals are very common on aircraft based in FL, and I would suspect the same near the borders with Canada and Mexico.