English hello (Hello's people may not know Americans use) Part 1 (Stay tuned for part 2)
Hiya is more of a informal one, when you say "Hiya!" It's more of a friendly greeting. But it also means "How are you?".
Sup can either mean "Hello" or "How are you doing?". Though it usually means "What are you doing?" or "How are you doing?".
3. How are you?
Yep, to Americans "How are you?" is more of a greeting then a question. When we say this we usually expect simple answers like, "Good! And you?" not "Oh, today was horrible! There was this lady...". Though if we do get a response like that, we'd listen, most Americans love to help!
I'm pretty sure this is a universal thing. If not, for people from countries that use "Hei", and "Hej", like, Finland, Norway, and Denmark, no it's not a butchered version of you're hello. It's simply a informal and shortened version of hello! Haha. :)