Speaking of not tasting the same, I've noticed differences just between Canada and the U.S. I've eaten at a few American McDonald's, particularly in the Mall of America, and the whole burger is bun! There's practically nothing inside... just bun, bun and more bun.
At least here in Canada they squash everything for you.
On a side note, in India, they have "Maharajah" pork burgers instead of Big Macs.
The McChicken Sandwich is the one that changes names the most, though, I think. In Norway, it's McKillig or something like that. It's odd how they'll leave stuff like "quarter pounder" the same, but convert other products to the local language.