They are not the same! The cacao differences between the two basically means the uk version tastes great, and the US one tastes like my socks.
replyAnd it's supposed to be called Marathon, too.
replyI've seen some YouTuber taste test both US and European Snickers, and he claimed they were quite different. Ingredients list backed him up.
replyEU had more peanuts, not so sweet and nougat was different, IIRC.