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 think you are very deeply mistaken. In 2014, when the annexation of Ukrainian Crimea took place, there were only 6,000 combat-ready troops in Ukraine, because Ukraine did not feel any threats and itself abandoned the world's third largest nuclear weapons potential. Therefore, the Crimea was captured almost without a single shot. In addition, Kremlin agents were in key positions in the army and law enforcement agencies, who gave the order not to shoot in any case.
Now the situation has changed dramatically. Ukraine has armed forces that occupy the 24th position in the world. Five Russian combat aircraft and a helicopter have already been shot down, two tanks and other military equipment have been destroyed. Putin will get a good rebuff and this will be the beginning of his end.