if you are not worried, you should be.
Business Insider has this post about the per capita car count per person of China relative to the U.S. and it puts them where the U.S. was in 1910 (if I could capitalize numbers I would for emphasis). An amazing statistic is that there 850 cars per 1000 people here.
I just got back from one of the most delightfully walkable cities in the world Dublin, Ireland. There is a certain joy in being able to move about on your own two feet to explore a place. Even if we do find an alternative to fossil fuels, we won't solve the congestion issues.