Will the US and Russia start World War III?
This sounds more like a joke than a question 
Last war United States won, or was part of the winning side, has been World War II that ended in 1945 (77 years ago). Ever since then US has not faced any actual military force and any other smaller conflict with armed groups US faced they lost miserably. The latest being the war against Taliban that ended with a great escape and a donation of $100 billion worth of weapons and military equipment to Taliban to buy safe passage out of Afghanistan.
Going to war with an actual adversary will not only destroy US military but also US and EU economy. That's why it is never going to happen.
I keep repeating this in all similar topics but this is not the first time Russia has taken part of Ukraine. Google Crimea and 2014 and see how people were asking the same question back then and how nobody could do anything about it. It won't be any different this time either.
What happens to bitcoin is unpredictable. Bitcoin is a great way to store value and is a replacement for traditional impossible to carry ways such as gold. It is not unreasonable to think people would largely start selling everything they have and start buying bitcoin to escape the crashing economy.
I very much agree. America, Europe and all countries under NATO will never dare touch this issue in Ukraine. This might force them into a very costly war and we can be quite certain they do not want this. However, there might be a wildcard hehehe, China. Might the western allies’ avoidance of war encourage China to invade Taiwan? It appears they might not have a choice. If the western allies send their military in Ukraine, China might join the war and invade Taiwan. If they do nothing, this might encourage China and invaide Taiwan.