Have you ever wondered what the Harry Potter characters would ever do if they were living in the Muggle World? I can't answer many of those questions for you, but I can shed some light on what the characters would major in, if they went to college.
1. Harry Potter- International Relations
Now, this one was hard to choose. After Harry leaves Hogwarts, he becomes an auror, and eventually is the head of the whole department. Criminal Justice doesn't feel right for him to major in, since he works with a lot more than that. Since he has to be diplomatic with what he does, and what he has done in the past, International Relations feels best.
2. Ron Weasley- Criminal Justice
Criminal Justice has always been the stereotypical lazy major. There's no denying that people with this major do a lot of work, but laziness is just what Ron was attracted to. He also becomes an Auror after the war for a good amount of time, reinventing the department with Harry, before he left to go help George with the joke shop.
3. Hermione Granger- History and Political Science
Nobody could ever hold Hermoine Granger back from accomplishing great things. After being the only one of the trio to go back to Hogwarts to complete her schooling, she started to work for the Department for the Regulation and Control of Magical Creatures. She changed the world and their opinions of house elves. After that, she became the new Minister of Magic after Kinglsey Shacklebolt. She had to work hard in her studies and possibly went to law school (in this muggle world fanstasy). The best way to accomplish this is to major in History and Political Science.
4. Draco Malfoy- Chemistry
Now, with Draco, we're unsure if he even would have gone to college in the first place. He basically just inherited his family's money, and he didn't really need to do much to stay rich and powerful. But he does go on to do a lot of alchemical work after the war, and even has the oppportunity to create his own philosophers stone but doesn't. The closest thing to alchemy in the Muggle World is chemistry.
5. Neville- Environmental Science
Some time after the war, Neville becomes the new Herbology at Hogwarts. Environmental Science is the basic equivalent of that. He is passionate about what he wants to do, and he also wants to teach others that they can be passionate about whatever and be successful in it.
6. Luna- Biology
After Hogwarts, Luna marries Rolph Scamander, the grandson of Newt Scamander, and she travels the world with him, studying magical creatures. So her major is Biology, with a subfocus of Zoology.
7. Fred and George- Business Administration
Obviously, Fred and George open their own shop, so they need Business Admin. But since you don't necessarily need a degree to start your own business, I assume that the twins, much like at Hogwarts, drop out early to open their business.
8. Ginny- Journalism
Ginny goes to be a player on the Holyhead Harpies before settling down to be a sports journalist, most specifically for Quidditch. Now, while they don't have Quidditch in the Muggle World, soccer is pretty close. This is why Ginny majored in Journalism with a subfocus of sports journalism.