England's monarchy began decaying about 800 years ago when King John signed the Magna Carta! It is nothing more than a figure head symbol today...the last semi-powerful world monarchy (besides those in the Islamic world) existed in Japan and I point out, unlike the Islamic monarchies, that it was only "semi-powerful" because Shoguns, war lords and, later government ministers (TOJO) really pulled its strings!
You forgot Nepal.