American porn stars, like the rest of American males, are most likely to be circumcised and those who aren't will usually ensure that their foreskin is retracted all the time the cameras are on them as that is how most Americans expect men to look. Non-American actors in porn destined for the American market will often also be instructed to retract for the cameras.
Porn made for the non-American market is also most likely to use non-American actors who are only about 25% likely to be circumcised. This market is more used to their males being uncircumcised and so far fewer of these actors will specifically retract for the cameras.
One must, of course, always remember that the foreskin is intended to retract for sex and so even uncircumcised men may look circumcised if only seen after they have an erection, even if they have not manually pulled the foreskin back.
Your foreskin should be able to be fully, freely and painlessly retracted both when flaccid and after erection. If not then you cannot keep yourself properly clean and there is also a strong possibility that the foreskin or frenulum may rip during sex with painful, very bloody and embarrassing consequences.