If we can somehow stabilize the spread of it, we'll be fine. West Nile Virus killed five people in Houston last year, and the world didn't end (except for those poor souls). There haven't been any SARS deaths in the entire country, yet.
But as long as the numbers are increasing in spite of all our efforts, it's a huge concern.
Don't get me wrong, I am concerned. I just don't think American society is as vulnerable as Hong Kong or Bejing. They may reach the number of cases necessary for the disease to explode. The numbers are still too low relative to the population to explode (as far as we know). If it continues to progress in numbers it may reach the point where everyone in Bejing will come into contact with it. That won't be fun.