The US won't export Abrams with the uranium armor and that's what is in storage. I doubt the US is going to change that policy.
There is a point where Ukraine is going to be pilot limited and training on the F-16 is going to take time. Ground crews need to be trained too, and that's a longer course than the pilot training. Even Ukraine thinks it will take 6 months minimum:
Ukraine says pilots would need six months for F-16 combat training
Ukraine probably had around 100 active fixed wing combat pilots at the start of the war. Their air force was not huge
Ukrainian Air Force - Wikipedia
They could probably scrounge some up from retirement and press people into service with related skills, but their pool of trained pilots is limited.
The US has about 1100 Patriot launchers, but only about 10,000 missiles. If Ukraine has a lot of launchers and are using them, they could deplete the stockpile pretty quickly.
The US does have a large stockpile of 155mm cluster munitions that will probably never get used again and ATACMS has been discussed at length. I think both of those could be delivered to Ukraine fairly quickly if need be. The US could also step up Bradley deliveries. Other weapons that could be delivered are US anti-entrenchment weapons. There is an array of weapons used by engineers to clear fortifications. A good stock of those would help Ukraine a lot in their coming offensives.
That is the tightrope Beijing has been walking throughout this war. China makes a lot of money from the US and Europe. If those western countries start switching to other suppliers China's economy will be in trouble.
In Russia Putin ensured that some of the wealth from raw resource sales trickled down to the population. Enough to make them feel their lot was improving, but the bulk of the wealth was stolen.
China's CCP has a sort of pact with the people that if they stay in power, the people can have the opportunity to get wealthier. A lot more Chinese wealth flows down to the common people than in Russia. China has experienced some instability of late because the flow has slowed down due to the economy maturing. If the west quits buying Chinese goods, that tightening will get worse and it could topple the regime. They need the west to keep the plates spinning.
Economically Russia is a treasure trove of resources they need for industry, but they are a tiny customer compared to the west. Russia has a population of 145 million with a much larger poor population than most western countries. There is very little market for Chinese consumer goods in Russia compared to the US with more than twice the population or the EU with an even bigger population. Both economies have large middle classes buying lots of consumer goods.
If the Russians allow it. Getting their hands on the Russian aircraft industry would help China with engine technology. That's the one area where China has struggled. Chinese aircraft designs aren't bad, but they have only just started domestic production of modern engines.