Is getting a visa to work at a U.S at startup something unique to the YC program? I am/was under the impression that the company had to be accredited to be able

Is getting a visa to work at a U.S at startup something unique to the YC program? I am/was under the impression that the company had to be accredited to be able to employ foreign nationals. Is there any advise you can give for a current undergrad (for me personally citizen of NZ and UK if that matters) to improve the odds of being able to accept a job or PHD study in the US (on the visa side of things), both at application time and now til then (~2 years away).