Language is alive

Where did I say it wasn't? But language being alive doesn't change history -- the phrase was used by British writers before the USA even existed.

and I can’t see anyone requesting origins specifically.

So? I offered the origin as it was presented alongside a number of phrases that are of American origin, and that one stands out as not (also as being suspected far older in origin than the others). I've simply added some additional information to the discussion. If you find it "boring", you are free to ignore it.

I didn't request your reply, yet you still wrote it.

Phrases like this can be part of 2 cultures at once.

Where did I say it couldn't? I merely stated that the phrase was not of American origin. I didn't say it wasn't used in the US, or that the UK somehow has some special exclusive licence to it.

and don’t even have hard proof one way or the other

I didn't post sources because I was short on time, but here, have some... (as I apparently now have time to waste...)

• "Dogs and Cats rain'd in showre", from the poem Upon a Cloke in Olor Iscanus (1651) by Henry Vaughan
• "...and it shall raine... Dogs and Polecats", from The City Wit, or, The Woman Wears the Breeches (1653) by Richard Brome
• "it should rain Dogs and Cats", from Don Juan Lamberto: or, a Comical History of the Late Times (1661) by Thomas Flatman
• "Made it rain down dogs and cats", from Cataplus, or Æneas, ... (1672) by Maurice Atkins
• "When it rains Dogs and Cats in Hell" from Maronides; or, Virgil Travesty, ... (1678) by John Phillips
• "raining cats and dogs", from A Description of a City Shower (1710) by Jonathan Swift
• "rain cats and dogs", from Complete Collection of Genteel and Ingenious Conversation (1738) also by Jonathan Swift

You will note that these are all British works by British authors. I can provide even more if you need them.

While the ultimate origin is unknown (there are many theories), any claim to it being American in origin is surely nonsense. There is no evidence for this at all. If you have some, please provide it.

What proof have you provided? Indeed, what has your comment added at all to the discussion? You could have looked up those sources and extensive etymological research on Google with less effort than you took to write your comment.

Pretty boring...

And what about your own comment? It adds absolutely zero additional information to the conversation, is rude, and you clearly misconstrued and misinterpreted my comment (apparently with the most negative interpretation possible), without even bothering to research anything for yourself.

Personally, I think some may find it interesting that a phrase they might have thought was of modern American origin is actually from another country and of far more ancient origins they expect. To me, that is interesting. If it isn't to you, why do you bother to read and comment?

In the future, I suggest you simply ignore comments you find boring and move on instead of posting insulting low-effort replies.