The Russian economic crisis does present threats and dangers to the United States in the event of a Russian collapse. The inability of the Russian government and businesses to make payments on financial obligations to United States banks is real, clean & present danger to the status of a fragile US economy.
A Russian collapse would be a good thing for the United States. We do not trust them, and they have taken over Crimea without justification. Hurting them economically would actually be a good thing for us, because it would bring them down as a power in the world. This is better than fighting a war.
Despite the fact that the Russian collapse will affect the US economy is one way or another I do not feel that it will be exactly "threatened" by this event. I believe it might affect our economic business but not so much so that the US should feel as if its future will feel a similar crisis because of it.
We should feel some what concerned about it, most likely will have an impact on our country in someway. We should definitely be paying attention to what is going on and have some sort of game plan just in case we do have some issues that come out of this situation.