The US must balance its - limited - ressources versus its needs regarding China. American weapon production also meets its limits, regarding production output.
The latter problem is shared in Europe, just that in Europe the deficits in military productivity are even much worse, and the willingness NOT to adress this in full is quite big in some key player countries, namely Germany, which refuses Macron's talk of European independence in military production (whether he really means it is somehtign different, when the French say "Europe" they implicitly mean "France first"...) and prefers to just crawl back under the American umbrella, hoping that Trump or Biden will play nice with NATO.
Russia on the other hand has raced at exactly the opposite direction: it has switched to full war production, and to such a total degree where it needs the war to continue at any cost, if the economy should not instantly collapse.
Two sides, the one searching desperately a way to peace, the other as desperately depending on avoiding peace and continuing the war to prevail.
Interesting situation, to put it this way.
As usual, my expectations of the future of this are utmost grim.
Also, a shortage of key ressources caps Western ammunition production.