An Absolutely Powerless king, yes.
And your point is? (Not that he has literally no power at all, although as king, Charles is probably meddling far less than as PoW.)
Being a non-native English-speaker, you are probably getting very confused, it certainly seems so from your posts.
Look up "constitutional" and "absolute" in terms of monarchy.
The UK is a kingdom and as likely as you'd ever be likely to get, united.
Are you arguing for an absolute monarchy? If so, I would suggest a move to the Russian Federation as that has got to be as close to it in a large country as anywhere in the world currently.
Even if the UK were not a kingdom, the name was just a choice of name. So far as I am aware, the British Empire never claimed to have an Emperor of the whole empire (Victoria was only ever called Empress of India?????), but it was called an empire. As above in several examples, a country's choice of name is reasonably arbtitrary - an excellent example is Rhodesia, which chose Zimbabwe, linked to one of the country's ancient and powerful tribes, which never ruled what the country is today.
Portugal is derived from the name of a settlement on the Duoro - a bit like calling the UK as a whole, Greater London, or Londonland, or Londiniumland, which, despite what many Americans in particular believe, is a (very) long way from being accurate.