Why do they call it a college degree and not a university degree?

Because in the US the schools that grant college degrees/diplomas are actually colleges, by the US definition of the word college. The US has both colleges and universities.

In the American Education system both Colleges and Universities offer 4 year bachelors degrees, the difference is that universities are usually made up of multiple colleges (college, of Science, College of art etc.) and may also offer graduate degrees.

to boot to most of the flaws human beings have offered as solutions, i've got discovered that college courses can commonly be longer than college courses. additionally, the prerequisite for a Masters application is a school degree. A Masters degree in reality makes you a professional in that field. relying at this methodology, college courses can encompass lots extra thought than college courses. many schools stress palms-on, sensible discovering.

In Canada we also use the British convention; it is an oddity of American English that "college" is used in general speech and in some formal contexts as well to refer to post-secondary education whereas in the same way we would use "university".

People here in the U.S. use "college" & "university" interchangeably, but in America there are Junior colleges unlike England.

UK and US education systems are totally different and incompatible.