You have to make sure the online courses you take are part of your HIGH SCHOOL education. Otherwise you’re no longer eligible for scholarships.
You can switch to a HS offering an AP or IB or A Level curriculum if it’s available,for instance.
With your whole transcript, you’ll need 4 years of English, 4 years of history&social science (geography, political science, sociology, psychology, economics…), math through precalculus and/or statistics and/or calculus, 1 each from biology, chemistry, physics or a mix of the 3 over 3 years +1 more year of science, and Korean language&literature, plus preferably 1 year of art history, performing arts, music, etc. All those should be at a level considered strong, like an A (a few Bs are possible). You can be homeschooled and take online classes but it has to be as a secondary school student.
Are there online Korean schools offering an English language curriculum (AP or A Levels) or IB?
You’re right it’ll be easier for you to be involved in the US film industry if you’re in the US. Right now, hotspots involve not just NYC and LA but also Atlanta for instance. In addition, many universities have solid contacts even if they’re not located there.
However there’s still a long road ahead for you. Remember that Korean film school may be more direct, since after Korean film school you could attend a US grad school for film too.
First step if you want to attend a US college, work through Khan Academy (free, online) and get the highest possible scores on the SAT. You need to practice till you score at least 1400, preferably higher. You’ll need a high score at most universities. You can take a test this Winter (Nov-March) to see how well you did with your preparation and recalibrate your plans if your score is disappointing.
Second step, you need to get a book called Princeton Review’s Best Colleges and find about 25-30 colleges you like. Because your grades aren’t very good, you’ll need to eliminate all the famous colleges but there should be at least 30 that work for you.