Kudos to those that noted the diference between camo and a uniform.
As for the reason the US Army wears woodland as a standard, it was developed and issued during the cold war. At that time it seemed the areas we were most likely to fight would be europe, south east asia, and to prevent communist expansion in central and south america. All places that the woodland works just fine. For that matter, it's good in most of our country and canada.
I have to say, I have always liked the woodland uniform, in fact I liked it better when it still had the skinny tabs on the waist. The new muti cam is cool, but I have some real issues with the extent to which they are using velcro and the zippererd front, don't even get me started. I think they could have done the improved pocket layout and all that, but kept buttons for everything.