One cup of tea? For multiple people? Mom, why would you do that?
(for each person) ;)
Can it have this distributive meaning?
I think that in Polish it rather means just one mug.
A more natural thing would be to simply say "przynosi nam herbatę", which is treated as a mass noun here and doesn't need to be pluralized to mean that everyone gets their own tea.
I believe mugs should also apply as you are dealing with a crowd and each will get their own.
I wrote " My mom is bringing a cup of tea." and it told that it was wrong and when I looked at the real answer it wrote "My mom brings us a mug of tea." like what is difference? ????
You've missed the 'us' part.