The position historically is a good deal more complicated than is described variously here. Prior to the 'Thirty Years War' in Europe nation states as we know them today did not exist. The Treaty of Westphalia in 1648 represents the beginning of the idea of nations which are synonymous with language ,and folk regions. Prior to that time most of Europe had been ruled by two major families, the Habsburgs out of Vienna and the Bourbons out of Paris. But the Habsburg Empire included not only modern Austria, Hungary, Czech Republic, Poland, Slovakia, Croatia, but vast areas of the Balkans, and also Spain, where a Habsburg occupied the throne. The Habsburg Emperor was also Holy Roman Emperor, and in that capacity held influence over all the states which make up modern Germany. The Bourbons governed most of present-day France, but perhaps less than half that region spoke a language which in any way resembled the French spoken in Paris. The Popes were also influential in greater or lesser degrees either side of the Reformation over the whole of the continent. The idea of 'nationhood' where you have a state of like peoples, speaking the same language, and with the same national icons and sense of identity starts to emerge after 1648 and reaches its apotheosis in the French Revolution: 'Allons enfants de la patrie'. In the 19th century great nations like Italy and Germany , previously only collections of Dukedoms etc were founded. The British Isles stands a little bit outside of this, and one can trace elements of an emerging national identity, for example, in the writings of Chaucer in the 14th century. But the English and Scottish monarchs intermarry with their European cousins, and George I who ascends the British throne in the early 18th century, as the first Hanoverian monarch is a German, whose first language was German.
Now languages are far older than this. Scores of languages were spoken in the old Habsburg Empire. To a large extent nations, when they began to be formed, were fitted around language groups. But there were many misfits, some of which would lead to the world wars of the twentieth century. The Balkans was a particularly difficult area, which has many national identities and had at different times come under the control of the Austrians, and the Turks, with Russia always having a claim to the Slavic areas like Serbia.
The whole scenario was completely turned upside down again following the First World war. At the Treaty of Versailles in 1918, a lot of new countries were created out of the old Austro/Hungarian Empire, with names like Czechoslovakia, Yugoslavia etc. But these were just arrangements of convenience which have not stood the test of time since they held different linguistic groups and different religious confessions.
So whilst today it is convenient to think of France and the French, Germany and the Germans, Netherlands and the Dutch, England and the English, Spain and the Spanish etc, it has taken a long time to get here, and much of the appearance simply papers over large cracks in the structures. On top of all this we now have the European Union which in some ways, if it eventually works, may take us back to something like the Holy Roman Empire with multitudes of languages, founded by Charlemagne in the 8th century (i think).
Hope this may help those of you who are Chinese and have not done much western history.