Do US universities look at GCSE grades?

Yes, they will look at what would be the equivalent to your full high school transcript for a US student - so both 6th form and GCSE results.

So u just have to pass GCSE eng and maths right?

You need to do a lot more than that if you intend to go to any university in the US better than one you could go to in the UK for less money.

Are there any alternative ways in which I can go to uni without my GCSE grades. .Also, what if I don't pass my GCSE (I got screed over by maths, and I'm still nervous for results day.)

If you haven't got strong GCSE grades I would suggest just focusing on UK universities as it's unlikely US colleges will be a viable choice once you factor in the financial angle.

Remember you will not get any funding from SFE to study in the US, and you will not be eligible for US federal loans either, unless you're a US citizen or green card holder already. You will be entirely reliant on the college itself meeting your financial need and most will not be able to willing to meet this outside of the most competitive and selective colleges, or on getting a scholarship - and the only kind that's going to fund more than a small amount of your fees will be a sporting scholarship.

So overall, you will almost certainly end up spending less to go to uni in the UK if you don't already have excellent grades if not also many other feathers in your cap. This is even before considering that UK SFE funding is pretty favourable as it's not like other kinds of debt and so doesn't affect you credit rating, is effectively impossible to default on, and gets written off after 40 years (or when you reach state pension age) in any case. Plus you don't make repayments unless earning over the threshold. So it may well be that uni in the UK is effectively free for you anyway.

Unless you are aiming to study at a really cut-rate college, pay out of pocket some very high fees, and effectively pay more for a worse quality of education than you would be able to achieve in the UK, it's not worthwhile.

Ok, got it. Are there any other ways to study at unis in the uk that aren't A levels? I'm just skeptical that sixth forms wouldn't accept my grades if they turned out pretty bad.