Comparing the world total by GDP is laughable. Single nations come out right. Russia 3.5, US 4.3 seems like a logical balance.
Also 2008, the stats year, is a bad time. We were in 2 wars and the rest of the world was cutting back. The following chart shows that were are spending very littel on our military in an historical perspective.
http://www.truthandpolitics.org/military-relative-size.php#gdp-graph
Even at a time of economic peril and global war we are spending very little on our military.
As I said earlier, or maybe in another thread, If Obama wants to cut the military let him propose it, and defend his decision. Clinton used gutting the military to acheive economic success.