There are lots of internet sites listing major differences between UK and US English - boot/trunk, faucet/tap etc - but I came across another huge minefield earlier -- flour types. Usually American recipes are 'translated' for British readers as the measuring systems are different (US uses 'cups' whereas UK uses grams), as are the temperatures (I have an electric oven, but understand temperature only in degrees Celsius; I also understand Gas Mark numbers, but I cannot fathom degrees Fahrenheit in US recipes).
I wanted to cook something that I found in a US recipe book, but was stumped when it said 'pastry flour'. In Britain recipes usually specify either plain flour (for bread, pancakes etc) or self-raising flour (which comes already containing a raising agent, such as baking powder, so is suitable for sponges, cakes etc). I googled 'pastry flour', but it left me more confused. In the US, as far as I could see, pastry flour seems to refer to a flour low in gluten. Well, the gluten content is rarely, if ever, highlighted on UK flour packs. Flour here in the UK is usually divided into 'plain' (sometimes 'strong plain' for heavy-duty loaves) or self-raising -- and that's it! You can buy wholemeal flour as opposed to white, but that, too, can be plain or self-raising.
I'm not a great cook, and my family don't expect a lot from my cooking, so I used plain flour in the recipe I was following (it was a sort of pancake where you added cottage cheese and apple to the batter mix - and in the UK I'd always use plain flour for pancakes). It tasted ok. But flour types are certainly a minefield. Cornflour is another misleading term. Here in the UK, cornflour is a very starchy product used in small amounts to thicken sauces, gravy etc. In the US, as far as I can see, it's another type of baking flour used in quite large quantities. UK cornflour is cornstarch in the US (this word is not used in the UK).
As for the spelling 'flour', it is related to 'flower; 'flour' was originally the 'flower' or finest part of meal, Samuel Johnson's dictionary of 1755 does not recognise a distinction between 'flour' and 'flower'.