The concept of the nation-state and nationalism are only a few centuries old. Before that we had feudalism, based in a set of intertwining personal loyalties rather loyalty to the state or nation as an abstract concept. In other words, the nation-state is not an organic part of human society but rather a construct created to meet certain needs - mainly economic ones and control of resources. However with the rise of capitalism, there really is less of a need to a state control resources. For example, France doesn't need to invade Germany to get German lumber - it can buy German lumber on the open market and Germans can buy French coal on the open market as well.
The side effect is that you don't have the nationalist wars you had in Europe during the 18th, 19th and 20th centuries which killed millions of people. So is the tradeoff of nationalism for peace and prosperity a good one?
You tell me.