There are a lot of high schools in the US that don’t offer math beyond Pre-Calc and some rural high schools that don’t offer higher than Algebra II. You’d be surprised how many rural schools that have less than 100 students…from K-12. They simply don’t have the tax base to support hiring a math teacher qualified to teach Calculus for one or two students.
If there is a “gifted” student in those schools, the State will usually place the child in a period of live, online instruction in the higher level of math. If the school isn’t subscribed to that service, then the student is stuck. It’s a shame, because some of these rural school kids may be academically capable of more challening math and science but it simply isn’t offered in their school. There are programs for kids like this to attend a community college for instruction, but the US is a big country. A 16yo is typically not capable of traveling 50 or a 100 miles to a community college.
Colleges will recognize that if a student simply didn’t have the ability to take higher levels of math and science, it’s not their fault. However, the student themself would have to decide if they can handle the course requirements in a top level school like MIT, CalTech, etc.
On the other hand, if a kid really wants to learn Calculus and College level Physics, there are ways online to study and then take standardized tests to receive credit. It’s up to the kid how hard they want to work to achieve something. To learn a task that might take 30min in a class, may take several hours online using Khan Academy or YouTube videos. But it can be done if the kid really wants to learn.