Russia will march on Kiev at the start and have shown if let, they would do it again.Ukraine has that option too. The people in the land Russia is occupying identity as Russian.
Now I suggest you open a history book and learn about appeasing dictators who want to invade other countries... It doesn't go well...
We stop Russia in Ukraine or US soldiers will be on the ground when Russia decides that a NATO country is next...
This war has cost US less than two month in Iraq war and it has US biggest enemy (which is not China) at its knees. Now is the time to send the message to Putin the war criminal that this is not tolerated.