"We" is a term that Americans use when discussing the actions of the collective of gangsters and plutocrats that control their government. So, for example, someone who has not even risen from his reclining chair will say, "We just invaded Iraq."

Even if there had been no United Fruit, and all pre-Castro Cuban business had been owned by Cubans, the fact is that they are now Americans. So it would still be valid to say "we used to own Cuba."