As things stand right now I will throw my thoughts out here and now, when it comes to Russia moving forward with its invasion of Ukraine it will happen and we the United States and the EU will do nothing more than protest and at the most put into place additional sanctions but nothing more.
The reason why in my opinion the EU will not get involved directly is that Russia has an energy strangelhold over them, Sanctions of some sort maybe but sanctions mean nothing when the natural gas gets turned off and you freeze to death. Russia while not quite the powerhouse it once was is still a very formidable adversary that you do not want to tangle with especially when they are in their own region.
With respect to the United States getting involved over the Ukraine issue I am leaning toward a very slight chance that the US gets directly involved, I do see sanctions as well as the funneling of arms to Ukraine as far more likely ( We are already doing this ) In summation the EU and the US just do not have for the most part anything to gain by going up against Russia in Ukraine and to be honest I think that by the time the world would be able to reach to the invasion it would be all over and Russia would hold most of the country and no world power wants to dig out a Russian bear.
China invading Taiwan for me is the larger global concern I believe this invasion will happen in my opinion, and the United States will be involved. Taiwan makes close to 90% of all semiconductor chips and has long been considered Chinese soil and they want it back for both reasons. We have all seen how China respects human rights and laws, ponder the plight of Hong Kong, Uyghurs, Tibet, and any other of the dozens of atrocities they have committed so you can only imagine how the people of Taiwan would be treated. Add to that the stranglehold the Chinese would put on the rest of the world when they have control of the semiconductor industry, this can not happen.
As I have said I do believe the invasion will happen and China will choose very carefully when they attack and again the United States, as well as several other countries will be drawn in. China must strike very hard and very fast to achieve this, they must overwhelm the defenses of Taiwan's land, naval, and air forces before US naval carrier groups can aid in defense. Japan has pledged support and following that England, as well as Australia, could lend support if in a position to do so. Indian may be a player as well considering their growing economic ties.
There is no doubt that one or maybe both of these potential conflicts may happen and the implications of the top 6 militaries (US, Russia, China, India, Japan, South Korea) all for the most part being involved will be huge, add into this 4 of these nations have nuclear capability and the potential for escalation while always there can not be discounted.
Stay frosty my friends.