I was having trouble finding quarterly breakdowns by region, but I did find a report that Switch topped 2 million units in the US around mid-October last year, and we know from quarterly reports that the console was at 7.63 million sold at the end of September last year. Based on that, it seems like US sales account for something in the ballpark of 1/4 to 1/3 of all sales, so there's a good possibility we could be looking at 4-5 million Switch units sold through December worldwide if US sales were 1.5 million.

That's just an educated guess, mind you. We'll have a clearer picture after Nintendo's Q4 financial results are released in a couple of weeks.