
you've watched one too many Russian army underwear model recruitment ads.
Ignoring other NATO country capabilities, the US alone has 14 Ohio-Class nuclear submarines at undisclosed locations around the world (they're extremely stealthy subs that are near impossible for other countries to track, and you can bet with what's going on the US has most of them in striking distance of Russia right now), and each one has the ability to launch 192 nuclear warheads (it only takes a few minutes to assign coordinates & launch). That's over 2,500 nuclear warheads (each one being 30x more powerful than what we dropped at Hiroshima) that Russia and China would never be able to take out in a first strike, exponentially more than Russia and China's nuclear capability in a first strike put together.
The US could wipe every major Chinese and Russian city off the map in a few minutes by pressing a few minutes. You're a colossal idiot if you think Russia and China could ever win a nuclear war with the US, even if they were the ones who struck first.