If patriotism means loyalty towards define borders, is it not better to think of ourselves as global citizens to serve mankind?

This is a romantic idea, which was propounded by Karl Marx. He said that all the labourers of world are united against colonial powers. But when the Second World War took place, all the labourers supported their own country. This is most natural that where I have been brought up and raised, I would love that land more than any other. Global citizenship is therefore an unnatural concept.