20 year old gap year student looking to pursue a computer science degree at a US university for September 2024

I am enquiring on behalf of my son who is in his second gap year after completing his A-levels and will be 20 in November. He got 2 As and a B in Physics, Mathematics and Computer Science respectively. He has been travelling the last few months but has decided he would like to go University to study Computer Science with a focus on AI in September 2024. He is considering both UK and US universities. Just wondered is he too old to apply to US Universities and are his grades acceptable for US colleges. Also, has he missed the deadling for entry for September 2024. Many thanks… Angela