I know there were celtic tribes in a lot of countries (Ireland,England,Spain,Portugal,France,etc) but nowadays we seem to only call celtic nations to nations that were never invaded by neither Romans, Moors, or Germanic tribes. So why are Asturias considered Celtic, but France is not, when both got invaded by Roman empire and Germanic tribes, and neither speak Celtic languages?
Because the modern definition of celtic was made by brittish people and it is just as random of a definition as any other.
You could argue that the fact they use a celtic language makes them more celtic but others can also argue their culture has been so diluted into the broader english culture the language is just a small thing.