Are 7A*s and 3A*s good enough for Ivy League?

My advice is to calculate your GPA. As per my calculations, your GPA should be around 4.6 on a scale of five. The minimum GPA required for Harvard is 4.2; for Stanford, it's 4.0; and for MIT, there are no official requirements, but above 4.3 will keep you safe. So as for now, I would say that you have a really good chance of getting admitted, go for it.

My advice is to calculate your GPA. As per my calculations, your GPA should be around 4.6 on a scale of five. The minimum GPA required for Harvard is 4.2; for Stanford, it's 4.0; and for MIT, there are no official requirements, but above 4.3 will keep you safe. So as for now, I would say that you have a really good chance of getting admitted, go for it.

US Universities, for the most part, do not do GPA conversions, so this is bad advice. Besides, the numbers you provided are more or less nonsense. Most schools convert to their own version of GPA, as schools within the US use different methods - particularly when calculated honours GPAs, APs, etc.

Are 7A*s and 3As good enough to compete for international places in US unis such as MIT, Harvard and Stanford?

Error in the title.

no. It would be very unusual if the top universities in that huge country happened all to be (relatively) close enough to each other that sports teams could travel between them even a hundred and more years ago.

The best, better 'best regarded', 8 universities in the United States would be (and only in the order that I call them to mind)

Harvard, Stanford, MIT, Princeton, Caltech, Yale, Berkeley and Chicago.

Your result is NOT good enough for London Metropolitan University, one of the lowest ranked uni in the UK, let alone top uni in the world. I am really amazed at people zero knowledge on higher education. Many still naively believe the GCSE/IGCSE alone is good enough for top elite universities worldwide.