I also found out that it is correct to say "Every family in the US owns a TV set." It is correct to use the singular in this particular case because we are not referring to the members of but to the family as a whole. I think every time the sentence would have the same meaning whe you add "the members of" before the collective noun, it is correct to use the plural.
Could it be possible that this is only a British English thing? I have never heard an american say "Have your family ever visited?" LOL