Most people from other countries seem to know, though they may need to be reminded. They laugh with me when I tell them we still have reindeer and snowflakes on our Christmas cards, even if it’s 30 C outside and we are having a BBQ and a swim in the pool for Christmas Day.
I think it’s very typical to see your own country as just one among many, and to be aware that reality is very different for people in different places.
People from the US though often seem to be quite insular, as if the world stops at the edges of the US landmass. I listen to a lot of podcasts, and it’s noticeable that a number of US speakers may describe something as ‘it shocked the world’ or ‘this world-famous sportsperson’ etc., when they are actually describing the US.