Not wishing to waste much time, effort, breath, life etc on this discussion (?) I would merely add a few observations:
1. Colonial America was so appalled by living under a monarchy that, when it tried to free itself, it offered a Kingship to a bloke called George Washington. When he turned it down (was it twice or three times?) they offered it to Charles Stuart, the Jacobite pretender to the British throne. When he turned it down they gave up and reluctantly became a republic;
2. Our beloved Royal family are indeed of partly German descent, but also are descended from llewellyn of Wales, and that should be good enough for anybody;
3. Thank God for the internet, so that all those rational people whose contributions I have read above cannot actually get at each other to break heads, lergs, bottles, windows etc.
4. If Britain ever makes the mistake of becoming a republic, it will find out to its cost what happens when you have a head of state who is a politician.
That's all --- you can carry on shouting now.