Both the UK and the US store listings just say "...limited to 4000 units." but when announcing the preorder for it, Ubisoft's website says,
"Limited to 4,000 units worldwide".
Interestingly one thing I noticed which is actually backwards to how I would imagine EU seemingly has so much stock is on US unboxings I seen there wasn't any platform specific sleeve around the case but on the EU ones I noticed that there was a sleeve saying PS4 or X1 at the top; I couldn't spot any PC ones though to see what they're like. (Of course that might just be a quirk that wasn't the same across the board but of the ones I watched it was the same in them.)