So yes, the current state of peace is unprecedented, though definitely not perfect.
... or as successful strategy. Those countries were considered 'rogue states' and enemies. Predictably, they are now failed states in which the diverse ethnic and political groups fight each other. No danger for the US any more. Mission accomplished.
If you look at a lot of the big conflict regions since then, they are often places that had conflicts under the surface that were contained either specifically by Soviet influence, or by the combination of Soviet and US influence because, while both may have sought to exploit opportunities from the bubbling conflicts, neither really was prepared to accept the risk of a major conflict getting out of control where they might lose key interests, and neither had enough local influence and power to be confident of attaining a positive outcome.
But the US's level of global influence through hard power -- maintained by military spending on par with the rest of the world combined -- is probably unsustainable, for much the same reason that the Soviet empire was (the US just started the hard-power spending war that was the Cold War from a much better starting point, and was able to carry it out longer.)