It goes without saying that blaming a country without specifying further is vague to the point of meaninglessness, regardless of how many of that country's citizens are culpable for the issue in question. But, obviously, such criticism usually arises out of desire for a clear scapegoat and is rarely meant to actually solve a particular problem.
To be honest, I have no idea how to eradicate the practice of blindly blaming entire nations. My hope is that the increasing contact countries have with each other in this era will increase intercultural understanding and decrease the primacy of nationality in people's identity.
It's just not that hard to take a little time and be specific with blame. When I travel internationally, I always hear criticism of "America," as if the 300 million inhabitants of one of the world's most diverse societies are walking in lockstep with one another. Simply ludicrous; indeed, Americans criticize each other far more intensely than anything coming from abroad. I'm sure people from everywhere experience this, but probably not nearly as much as an American at this point in history.
It's like the story of the American diplomat chatting with a worker at a Russian train station. The diplomat commented that the train service was very slow, and the worker responded, "Yes, but in America you've lynched Negroes."