Is it used nowadays like an intensifier?
It's raining like anything
She studied like anything to pass the exam
People in the USA will know what you are talking about, but no - "like anything" is not used often.
Like anything? I have never heard that phrase.
"It's raining like cat's and dog's." is common.
I've seen that a lot of things are used to compare. He studied like a horse, for example. The "horse" is used for emphasize a vast content, probably due his big aspect. When I want to compare something with a word and it doesn't pass through my mind, I usually say: "It's raining like I don't know what!".