In Ukraine? Nothing beyond supplying them with high-end weapons. Putin probably isn't too keen on starting a war that could turn into a 21st century version of Afghanistan. For Taiwan, I think we make it clear that we will not yield Asia up without a fight. The PLAN isn't anywhere near being a blue water navy, yet. I'd hope that Xi is too risk averse to chance having most of his shiny new Navy sent to the bottom of the Taiwan straits. OTOH, if we positioned a carrier group close enough to do them damage, those hypersonic weapons could send a few thousand sailors to the bottom and THAT might well trigger a nuclear exchange.
It's the uncertainty and the chance for Xi to miscalculate Biden (or his puppet master's) response. One thing is sure. If Xi decides to go for it, he won't be able to back down. FTM, neither could little Vladimir Vladimirovich.
Dangerous times ahead. Our enemies from Iran to the Norks, to Xi, and Putin are going to be seriously tempted to take advantage of America while we are in such obvious disarray and chaos.