History books may use rhetoric and formulate expressions as if «populations made choices». But since really populations do not make choices, one should avoid throwing in one's mind abstractions before translation to the literal truthful statements, for mental hygiene.
It was not the European population to put presence in the MONA, not Richard's brother, who even voted against, to cause brexit: they are not responsible.
Surely history will act with stochastic determinism, creating maybe an aura that one may romantically depict "as if responsibility" - but in a future wave of damages involving the real Tom and Dick, they will most probably be innocent. What they could have done to prevent facts is minimal. Let us just be careful in spreading slogans that weaker minds may take literally - it would be an damage against a very real mental collectivity, more and more people seeing the false instead of the truth, using bad intellectual keys with collective consequences.
In fact, the chief thing one is responsible for in these matters, is the ongoing effort towards cultivation and refined intellectual discrimination and judgement. Little, or much less, can be done for the neighbour - surely let us not pollute his mind.
Again on the specific point:
responsibility means that somebody should respond with consequence to some event, in fairness and justice.
-- Officer Greene is a policeman. He may kill an innocent in action. He is responsible. In case of incident, he will be investigated, there may be consequences on his career, reputation, freedom etc. That "Officer Greene is responsible" is true and meaningful, makes sense, to an easy interpretation of the statement.
-- The team of Mr. Browne organizes business continuity in an office. They are responsible. In case of incident, they will act and be judged for it, as their good or bad work prevents or causes losses etc. That "Mr. Browne's team is responsible" is true and meaningful to an easy interpretation of the statement.
-- If one stated that "the people are responsible for the action of the elected", an interpretation should be provided that makes the statement true and meaningful. Good luck with it, if anyone wanted to tackle it - I do not see it easy, nor possible.