How hard is AP Calculus AB compared to college calculus I

It isn't so much that one is "harder: than the other, it is the amount of time you have, or the speed of the class. In High School, you have two semesters to get it done, whereas in College, classes last less than one semester. So in College, you have about half the amount of time to learn basically the same material. Also, you will not see your College teacher nearly as often as you will your High School teacher. I would discuss this with your schools dual-enrolment coordinator.

You are coming from a different country and it was a long time since I took calculus in high school, so we may be comparing apples and oranges.

I took calculus in high school, and then took it again in college. I thought it was considerably more difficult in college.

I did not take it in highschool, probably should have but i took the easy route and took AP Stats.
Then took calc in highschool a year later and it kicked my butt.

But if you have a background on calc knowledge it should be really easy for you

AP Calculus is a bit more difficult since teachers at high schools expect hs students to learn more than college students.