I don't know how good for the world it has been. At least it has provided a long era of... something near to peace, specially compared to the past.
Now, for itself sure it has been quite good, it set itself as the leader of the world due to the dependency it created and allowed it to manipulate international politics as they wished, and this is one of the things I see the USA losing and some other power taking advantage of (replacing the USA in this position).
There is 3 countries that basically do whatever they want in the world (and it's not always diplomatic): USA, Russia, and China
All of them have some poor diplomatic moments: Iraq, Crimea, and South China Sea
I don't see any of these wanting to change the status quo. Especially since we are already starting on a better relationship with Russia.
