The two major regional contingency capability (which was not a strategy, but a principal notionally underlying national security strategies for a couple decades) was concocted in 1993 as, basically, political cover for massive defense cuts -- that is, it was saying "despite the cuts, we will retain this capacity" -- and was very quickly recognized as a largely fictitious capability [0] especially as the US fought major regional contingencies after that point and it was clear that it could at most prosecute one effectively and be prepared to engage in a holding action elsewhere [1], even when "major" was much smaller scale than war with Russia or China, and was formally abandoned in 2012.

[0] Part of why this recognition was because the formal documents outlining the concept and how the capacity would be met had caveats which indicated that it wasn't really a capacity to fight two MRCs effectively and simultaneously.

[1] "Win one, hold one" was described as the likely best-case actual capacity years before the overlap of Afghanistan and Iraq conflicts concretely demonstrated the lack of genuine two-MRC capability against much less capable foes than Russia/China.