Russian forces have invaded the independent and sovereign nation of Ukraine - changing the norms of modern geopolitical politics

Russian forces have invaded the independent and sovereign nation of Ukraine - changing the norms of modern geopolitical politics. This event will have adverse consequences on Europe and the United States (military, politically, and economically). Many argue Russia's actions resemble Germany's aggression, in the Rhineland, Sudetenland, and Poland, leading up to WWII.

Knowing that Russia is a member of the world "Nuclear Club" and has the technology to strategically target American cities and assets around the world with exacting accuracy, how should the United States, NATO, and our allies respond? What reasonable tools do we have? What do we think is Russia's goal? How will this end? What is America's role in this situation? Consider and discuss the economic effect on the U.S.
In at least a paragraph or so, please answer the questions posed with facts and reasonable analysis. Do not respond with garbage like "we should wipe Russia off the face of the earth".