Putin decided to invade Ukraine, and no one can stop him including the US.

US President Joe Biden says Putin has made a decision to invade Ukraine and moved Russian troops in an attack position to invade. 

The Biden Administration has made serious mistake about Afghanistan's withdrawal and has emboldened the Russian military might and allowed them to invade the smaller neighbor country.   

All the dictators are watching the US leadership and unfortunately, Biden weak leadership causes many chaos around the world from the inflation, drug abuse, to an invasion. Since Russia doesn't care much about the world's sanctions put on his country and is now making move to invade Ukraine is a proof that sanctions don't work on dictators. It created more harm to the civilians than the government itself.  

If the Russia military successfully invades Ukraine because of US weak leadership, China will be next to invade Taiwan. It will be all depending on the US military power and influence around the world. So if US cannot stop one invasion from the dictator  of Russia, it cannot stop invasion from the dictator of China.

The only way to stop an invasion of Ukraine or other places around the world is to negotiate from the position of strength and punish the invaders with the US military power. That is the only way to make the dictators listen and think twice before making their moves otherwise they don't care regardless of what sanctions the world put on them.