[Thats a good question. It is definitely the Pacific and those spikes are on the US side. Not sure why it is designed like that though.]
They can’t screw with it from the ground on their side. They actually have to climb up the wall and over before they hit the wire.
In that pic, you can see downward pointing spikes on the US side. They look designed to make it hard to climb up from the US side - which is a bit odd.
Also regarding the razor wire on the US side. I'm sure that is why it is on the US side - to make it more difficult to screw around with. But it doesn't seem that difficult. Especially once you realize that the "wall" isn't really a wall. It just looks that way in the photographs that are conveniently taken at a sharp angle. Have a look at this one: