There isn't really a short answer to this - it really depends on where you live.
There are absolutely loads of differences. My personal experience overall is that our US schools focus much less on things like uniform, hair colour, not eating/drinking in class, and much more on things like overall behaviour. You can wear ripped jeans and pink hair to school and no one bats an eyelid, but if you turn up drunk to a school dance you're in severe trouble.
Where I am at least the teachers are better paid, and much less stressed than in the UK. We have class sizes of 10-25 depending on the grade (and our schools are classed as overcrowded which always makes me laugh).
Kids are not streamed so soon, and to a great extent especially at high school they can choose whether to take regular or advanced classes. A really smart kid may end up going to a magnet school where they will be stretched much more - usually at no extra expense.
There isn't the pressure of GCSEs and A levels, but there is an expectation that not only will you work hard to keep up your average score (GPA) but you'll also have lots of outside interests - often it's those outside interests that get you into the best college.
You take a general education right up to 18, rather than specialising in an ever decreasing number of subjects.
There is much more sports, and also IME a much closer school sense of belonging and culture.
School acceptance is done strictly by catchment area at least where I live, and if the school gets overcrowded they will build more on it.
No one gets chickenpox, and it's very unusual to get measles, as they are much more aggressive with insisting on vaccinations.
Things like getting to school are easy because there are school buses and plenty of adequate parking. Out school day is 7.55am to 2.55pm, and there's after-school care, which makes it fairly easy for both parents to work.
OTOH they have VERY long summer holidays. But there are tons of summer camps.
I am only really speaking of our school system though.