Opinion and reputation have little to do with national power, George Friedman notes:
Whether the US president is loathed or admired is of some minor immediate import, but the fundamentals of power are overarching. Nor do passing events have much to do with national power, no matter how significant they appear at that moment. The recent financial crisis mattered, but it did not change the basic geometry of international power. The concept of American decline is casually tossed about, but for America to decline, some other power must surpass it. There are no candidates.
From a military perspective, I suppose that zero-sum analysis makes sense, but I’d hardly dismiss economic decline as a non-issue, simply because no other nation has yet surpassed our standard of living.