Do we know how much Switch sold in the US by the beginning of December? We can use that information to calculate the December sales in the US. The charts unfortunately only show regional data in the US up to November 18.
If we conclude from the NPD data for November, it would put switch sales in December at around 1.4 million.
Edit: we didn't get NPD for switch, but could conclude from reports on PS4 numbers and switch selling half.