GOP warning of ‘national security threat’ is about Russia wanting nuclear weapon in space: Sources::The White House will meet with congressional leadership as a top Republican is requesting President Biden declassify information on a “serious national security threat”
One of the things about New START is the US and Russia inspect each other’s launch capacity, and its a bit of a zero sum game: The US would never admit it has better launch capacity against Russia because it tells China and Iran they can sweep in and gain soft power. The US could admit it and then the rest of the world sees a hyperpower situation again and a need to de-escalate its own capacity.
They wouldn’t though, even if 5% of their missiles/nukes work, millions would die.