How I'm earning a bachelor's degree by 18

[RANSOMSOUL]

Sorry, but college is much harder than HS. Even AP courses run at half the pace of a college course. Yes there are HS students who can handle a college course or two, but it is definitely not a majority.

It's not an unbalanced position to challenge the comparison in the difficulty with HS vs College. There are a few factors that could heavily influence HS actually being harder than some courses (e.g. general ed/electives) My daughter graduated with a 4.7 in high school and her workload was off the charts. However, she is now testing out (pass/fail) with the majority of her college courses (general ed/electives/major math), she feels the workload is less than half. Now, if she was gunning for A scores (90%+) then she would most likely feel some additional weight in prepping for exams. There are of course certain specialties that by default are considerably harder in college (e.g. biology, physics, engineering) but even with those, it's dependent on the student's skills, they may not feel a significant bump in the challenge. 

With all this being said, by average, I completely agree that college is harder - take an average or poor high school student, place them in college and they are sure to be completely overwhelmed in their first year with the new workload. Homeschool kids are outliers when measuring the difficulty in college and I am not surprised the OP isn't feeling that much weight with the task at hand.