Power..

 

Paul Kennedy posits that continued Debt and deficit spending, especially on military build-up, is the single most important reason for decline of any great power. 

The costs of the wars in Iraq and Afghanistan were as of 2017 estimated to run as high as $4.4 trillion, which Kennedy deems a major victory for Osama bin Laden, whose announced goal was to humiliate America by showcasing its casualty averseness and lack of will to persist in a long-term conflict. 

By 2011, the U.S. military budget — almost matching that of the rest of the world combined — was higher in real terms than at any time since WWII.

Kennedy made similar assessments about American decline in his book The Rise and Fall of the Great Powers in which he projected "a need to 'manage' affairs so that the relative erosion of the United States' position takes place slowly and smoothly".

Now with other countries advancing like China and India, the BRICS coalition which 

control 43% of World GDP, the deDolarization aspect of the trade and finally the oil/Energy control, No war, all will have a great impact on the current 

G7 decline.  "Its the Economy Stupid"