Americanisation - A Colorful Mistake?

Americanisms are the one thing that can cause controversy in the British-English language. Why? I don't know.

I don't understand the argument some people make of English people having prior rights to the language, and anyone who doesn't fall into that category is an 'interloper' who is trying to take over the language. Why do we, as the British people who apologise for anything and everything, feel as though we have to be so defensive over words, that we will call out anyone who is even partially incorrect?

One of the most argued points is that Americanisms are ruining our language, but how can they be ruining it when some of the words we use most often are Americanised, meaning that some of them are accepted. Is it because they're beneficial to us, or because we don't have another word for the same thing, or even because we don't know that they're Americanised? When we already have a good enough word, such as biscuit, why would we need the word cookie? Or the spelling color? This argument makes us seem unaware and uneducated about the origins of the language we so proudly call ours, with British-English speakers even taking credit for the words we "borrowed" from another part of the world but made it ours by changing one letter. This is just the first sign of hypocrisy in our language.

The British people love to point out all the Americanisms that they see, immediately commenting that the language is ruined, but do they do the same thing when they see the words that we have taken from all over the world? Shouldn't the words with Chinese, Indian and Arabic origins be treated the same way? Or is it okay because we want more power, or because or because we have influence as a country, so we can take whatever words we want? Are we, as a country, threatened by America, who is bigger than we are? Do we not want them to take over our language, just like they have done with so many other things? Some things from America I would enjoy being over here, but others... not so much.
Or, is the reason we hate the Americanism of the British-English language a less political case of just wanting to avoid confusion with spellings and ambiguity of certain words? This could be the case when trying to teach young children to read and write, and there are words with multiple different spellings and meanings, which make the process a lot harder. This could result in them using the wrong spelling and being confused when it is corrected. Another example of the ambiguity in the language could be when a British-English and American-English speaker are communicating and there is confusion around different words. For example, Pavement means two different things, depending on what English you are speaking.
For me, the Americanisms of the English language isn't the worst thing to happen to us. Yes, some words have different spellings, but is that what we should be worrying about right now? The American-English adds some enthusiasm to the plain British-English, and shouldn't we be ambracing all different cultures anyway?