They may have a billion people but they are concentrated in a small area , like the bulls eye on a target .
Not at all, their population is widely dispursed. Here is a list of the 10 most populated cities in the world...
1. Tokyo, Japan - 28,025,000
2. Mexico City, Mexico - 18,131,000
3. Mumbai, India - 18,042,000
4. Sáo Paulo, Brazil - 17, 711,000
5. New York City, USA - 16,626,000
6. Shanghai, China - 14,173,000
7. Lagos, Nigeria - 13,488,000
8. Los Angeles, USA - 13,129,000
9. Calcutta, India - 12,900,000
10. Buenos Aires, Argentina - 12,431,000
As you can see, China with a population 3-4 times ours has 1 city and the USA has two. The US is actually much more segregated in its population (Urban/Suburban vs. Rural) than China. We are much more "bulls-eye" oriented than they are.
They have nukes but so far they don't seem to have a good delivery system ( read accurate by our standards ).
They have delivery systems in every strip mall in the US. They're called Chinese food restaurants. Why spend billions on designing a rocket that can be detected and shot down when they can simply ship 10-20 warheads over here, have them delivered to the sleeper cell restaurants and time them to go off at the same time. Imagine losing NY, DC, Chicago, San Antonio, Houston, LA, Cincinnati, Miami, St Louis, Detroit, etc in the span of a couple of minutes. If we can't stop random illegal aliens with no education from crossing our border, what are the chances of stopping a dedicated enemy?
Then also consider we are the only nation to attack an adversary with a nuke PERIOD !
ASK JAPAN was it worth attacking the U.S.A. !
Japan didn't have nukes.