I woke up this morning with a thought.
Is it a good idea to split the different media queries in different files, check the width of the page in functions.php and then with an IF call the "correct" using
There are no functions in wordpress that checks or determine screen sizes. These are all browser related stuff that has got nothing to do with wordpress. There are jquery functions that can maybe work, but again, this is not wordpress related.
wp_is_mobile can be used to load stuff conditionally for mobile phones, but then again,
wp_is_mobile don't have the logic determining screen sizes, it also can't differentiate between things like mobile phones and tablets.
Your solution here is to do it old school, using media queries in your main stylesheet as done in all of the default themes shipped with wordpress.
Closing off, I would most probably think that if there was such functions to determine screen sizes in wordpress, that it would be completely overrated and useless and time wasting just to load something simple like a stylesheet