Why is it called University in Europe/Australia/Asia but College in America?

It's not. That's a misunderstanding of the terms. A university is an institution made up of several colleges. Within a university there may (just making up examples here) be a College of Letters, a College of Sciences, a … um … College of Dentistry. Whatever. I attended the University of Southern California, but I spent most of my time there studying in the College of Cinema and Television. (For historical reasons it was called the School of Cinema and Television, and I think it's since changed its name, but it was a college within the university.)

In the United States we have universities which are made up of distinct colleges, but we also have colleges which stand alone. Some young people attend universities and study at colleges within them. Other young people attend colleges.

Another strange thing that I've noticed about this. In America we use college as a generic term. "Where did you go to college?" "I went to New York University." We would never ask a person where they went to university.

Also, in the UK they don't use the definite article when speaking of a university. "Whilst he was at university..." Whereas, we would say, "While he was going to THE university." (For some reason the same is true of hospital - in hospital vs. in the hospital). Yet, we would say "While he was going to college" but we woul not say "While he has going to the college."