LOL! No, why? The wiki entry will tell you the same thing
http://en.wikipedia.org/wiki/United_Kingdom
Why all the different tags? Well you need to look at how the UK was formed and what the various nations were like before they became part of the UK.
I'm guessing, but I'd say you're from the US?
Well, put very simplistically, imagine a smaller USA with just 4 states. Each of the states joined the Union at different times and each state was formerly an independent country (with the exception of Northern Ireland which was formed by carving up someone else's country into smaller pieces early in the 20th century).
So ignoring Northern Ireland for the moment, as that's a bit more complicated:
So lets take three of the four corners states. We've got Colorado, New Mexico and Arizona and they all form one sovereign nation. Each of the states has its own culture and history and was at one time under its own rule. Just because the 3 states are now under the same government doesn't mean that Colorado will stop being Colorado, or that Coloradans will stop being Coloradans. Hence all the different tags.
I'm Scottish, and many of us will describe ourselves as Scottish before we'd ever describe ourselves as British. (Worth mentioning again that British does not mean English.) Scotland was an independent country for over 850 years before we 'joined' the United Kingdom in 1707 and the other countries which make up the UK all have similar histories. We might be all part of the same union now but we're all nations in our own right. It's not unsurprising that we all maintain a national identity.
Well that was a longer reply than I intended, but basically this group of islands has a long history and you can't really throw all that away and just use the one label of "United Kingdom".
:wave2: