How hard is it to switch majors as a transfer student within the College of Letters and Sciences?

Like if a student were to switch from something like the Classics to like History, and they have all the required courses done in CC, we he be able to do it?

Yep, it’s very easy. Everyone in L&S comes in undeclared. If you mean switching after you’ve declared, people would usually just double major but it’s not too difficult either way.