I have heard that XSeS is available on some places of USA too.
But it is definetly available on many european countries, and for series x it took weeks to be sold out on many countries, unlike PS5 which sold out in seconds/minutes.
So yes, story goes that series s+x falls behind xbox one AND is not completely sold out.
I'm pretty sure that it dont sell epic numbers at EU too, while it may be sold out or hard to get for a while (xsex), compared to PS5 which seems to be sold out for next 2-4 months on many areas