If Biden make mistakes it will lead the West to begin the World War 3.
I don't think Biden would intervene, he knows that Putin is suicidal and he is not ready for the WW3. All the US can do is to impose sanction economically, and they will not involve in that war between the two countries, in short, their support is very limited only.
I don't think Putin is suicidal. Maybe a wee bit. I feel he's just fighting to protect what's his because should he fold his hands and do nothing, the US could through persuading Ukraine to join the NATO get to them. Although staging a war is not the best method of approach, I guess he saw no other means but to use war.
Of course Biden can only look on while the Ukrainians are being ravaged because frankly, he does not want his head on the chopping block should a more severe outcome like WW3 occur if he as much as lends a hand and I think Putin is aware of this. This is more like checking a king!