To get some view into why, take a look at the emergence of the AIIB (China's equivalent of the World Bank) and take a look at the reasons why the US has been in negotiations in Iran (Just about nuclear proliferation? There's a bit more to it... http://youtu.be/hs_2zzNyP_M ).
In short, the strength of the US Dollar is seen by quite a few people to be based on its position in international trade, and this position is being challenged (past challenges have led to wars, but that's not going to work for much longer, unless the US intends to start WW3). If the funding base is taken away, the US military is unlikely to remain the dominant force it is today.
Kind of puts the TTIP/TTP/TISA deals into a new perspective too, international deals to reassert the US position by boosting the role of big business.