Have you ever wondered why Americans and British/Aussies spell English differently? How are colour and colour the same word? Centre and center? What's up with that? It's all thanks to Noah Webster (yeah, the Webster of Merriam-Webster). When America gained independence, Webster wanted to simplify unreasonable spellings that were handed down from the British.
Webster went a little bit too far when he made his first dictionary though. He dropped silent letters so words like "determine", "leopard" and "soup" became "determin", "leperd" and "soop". Some of his spellings obviously never caught on, but the break from Britain's English essentially started there. Some caught on like cutting U's from "colour" and "flavour" and putting R's after E's in "centre".
During that time, the Brits doubled down on their way of spelling and basically scorned at the new American way of spelling (though they did drop the -K in words like "magic"). They kept their spelling as America changed theirs. It's a fun bit of language history to learn about. Watch as Arika Okrent explains below.