There's lots of other viruses making the rounds in winter. This timeline doesn't add up; December is way too early for COVID-19 anywhere except Wuhan. It was something else.
It's hard to tell without testing patients, of course.
But with unrestricted intercontinental flights spreading diseases requires bad luck, not time: in December (or earlier) the streets of Wuhan and any city in the world were only one cough in the street apart.
It's still doubtful though, since there was a small number of people infected, the odds of them in particular traveling while contagious are low, especially when you consider that the first people infected may have limited travel because of demographics.
For December time frame, this is the correct interpretation. We would already see a suspicious spike in 1st-2nd week Jan pneumonia death rates if COVID-19 were spreading in the US in December. Average time to death for those who do die is I believe 17 days from onset of symptoms.
Yeah, there's just no way there was a huge COVID-19 cluster here in the US in December, and then everyone just got better and it never turned identifiable. We know how insanely contagious this disease is. It couldn't have been circulating for months in a given area without sending enough people to the hospital/morgue to draw scrutiny.
