Hiroshima......current population 1.4 million 15 kiloton bomb
Nagasaki......current population 450K 21 kiloton bomb
If the soviet strategic nuclear forces perform as well as their conventional military forces I'm not sure we have much to worry about. China owns our debt they wouldn't make a strategic play. In a limited exchange or isolated incident radiation levels drop extremely fast outside the blast zone, 24-48 hours (80-90% drop), then 1-2 weeks(95-99% drop), if you didn't get burned by the flash you will probably survive the event. If you don't breath it, eat it, wallow in it and hide from it behind or under dirt, concrete or stacked up books, for a relatively short period of time you will survive the fallout if you weren't able to evacuate.
The chaos that follows with the possible lost of Facebook, Instagram, Twitter, Tik Tock and ARFCOM may be too much for many of us.