Biscuits in UK are flat round kind of cookie like, but not a cookie. Not what US calls biscuits, especially not the kind they call biscuits in the south

In USA I think people dunk donuts or other pastry into coffee, at least that's what my parents did. Young folks seem to have lattes and other high calorie coffees that do not need anything extra to dunk. At least when they get coffee to go from coffee stops. Coffee is like beer over here. There's so many aficionados here that many homes grind there own and have their own preferred methods of making them. My ex used to use a cold press, I've known others who love percolated coffee although it's hard to find now. My daughter takes after my ex in that she's fussy about coffee beans and how it's made but does drink herbal teas too.

Personally I don't dunk anything in my teas but sometimes I get UK biscuits from the store and do dunk them. There's something more duck able about them.