For me this is an interesting question.
I, although American, have lived most of my adult life abroad. Growing up we had 7Up. In fact, although not large soft drinks consumers, we always seemed to have some in the house. We often used it if we had an upset stomach.
Now living abroad, I have never seen 7-Up only Sprite. The Coca Cola brand is strong here in Brazil as it was in Europe.
As for Sierra Mist, I love the name but have never tried it.
In Britain, where I lived many years, they call these types of drinks 'lemonade'. As Americans we know lemonade and a 'lymon' drink are world's apart.