The US is indeed facing two nuclear armed peer adversaries in China and Russia which are projected to have combined as many as 11,000 strategic and theater nuclear warheads by 2035, some multiple thousands greater than their combined number of warheads today.
A key question is to what extent do nuclear weapon numbers matter? Certainly, they should in any treaty which mandates force levels, although the 1972 SALT I limits on ICBMs and SLBMs were unequal in Russia’s favor. But in the seven proposed strategic nuclear weapons treaties between the United States and the USSR and then Russia, numbers of warheads allowed for each side were the same although deployed differently.
A 1983 US government assessment noted that prior to the first arms deal, in 1965 the US had 6000 strategic warheads vs the USSR at 600. By 1983,the assessment further explained, after the SALT I/II treaties of 1972 and 1979, respectively, the US had 8900 strategic warheads and the USSR had 7800. And at the time the assessment projected that by 1993, absent arms control [such as the proposed START agreements to reduce nuclear weapons], the USSR would have between 14,000-23,000 deployed strategic nuclear warheads.
Looking forward, absent new arms control agreements, the 2010 New START agreement expires in February 2026. The future nuclear balance may be very disparate even after the current US nuclear modernization plans are completed. That may have political consequences with the US public, Congress and our allies.* And may lead our adversaries to miscalculate and take risks threatening US interests.
However, if the United States has sufficient warheads to cover all of the targets of deterrent interest in Russia, China, and North Korea (plus a reserve), does it need even more nuclear warheads above that number simply because the Russians and Chinese forces combined are much larger?
The Posture Commission of October 2023 addressed this question and concluded that while the US may need a greater future nuclear deterrent capability, the United States did not necessarily have to match the Chinese and Russian nuclear weapons forces “warhead for warhead” for targeting/deterrent purposes while also concluding (with strong caveats about the future) the US nuclear deterrent was strong today.