Context: There are two families. Family X have a car each, and Family Y also have a car each.
Can “two families have a car each” mean “A, B, C and D have a car each”?
I mean, families are regarded individually here. In this case, can each of families be also re-regarded individually?
Or can a collective noun be considered individually only when a collective noun is singular?
If two families have a car each, each family has a car. That's to say there is a total of two families and two cars.
If A,B,C and D are involved, there are presumably more than two families concerned. Then you need to rephrase your question.
If all four families have a car each, then each of the four families has a car. There are now four families and four cars in total.
The number of families is not really relevant. The only question you need to ask is whether each family has a car.
If individual members of those families have their own cars, then the question is whether each member of the families has their own car.
If I have misunderstood your question, can you please make it a little clearer.
No. "Two families have a car each" means just that and no more: there are two families, and each family has exactly one car. In this situation there are two cars.
If A, B, C, and D all have their own car, you must say
Two families have two family members each. Each member of each family has a car.
In this situation there are four cars.
