What would you call "Public Viewing" (people watching football match) in English?

Solution 1:

Public "screening" implies a recorded or captured event reproduced or distributed for viewing by a disparate audience. You're watching a screen or a projection of the event.

The implication of a public "viewing" includes events taking place live and in person and not for view outside the venue where the event is taking place. As there is no device mentioned, you could be viewing virtually anything in a place reserved for you to be during the activity.

There seems to be no reference to the temporal in either case although live events would be without delay caused by the technology required for the event availability.

Solution 2:

It also depends on the location. But depending on the situation, you could easily just say watching the game. Like: "I always watch the game at my local sports bar." "Do you want to go watch the game with me?"