What are the requirements to apply for a Phd. in the US?

The broad requirements would be transcripts, GRE scores, the application itself, and perhaps writing samples or a professional portfolio. If there is anything else, the program’s web site will probably explain it.

Somehow you will need to certify your previous degrees’ coursework to show if (and how) it meets U.S. accreditation standards, and if you’re from a non-English speaking country this may require translation services. I would guess this would all be explained on programs’ web sites too.

PhD programs are each specific to the university that offers it. And the selection is more personal than just submitting grades and test scores. And each differs depending on the discipline; getting accepted for a PhD in a science is much different than in a liberal arts program.