Coming from a comedian who job is one of the least effected by immigration. Its hard to be a comedian if you don't grow up in the country (No Canadian comics don't count).
I remember seeing Eddie Izzard in Slovenia. The fact that he's from the UK, not from Slovenia, did not seem to detract one bit from his famous Darth Vader joke.
Russel Crowe is also a great example of a comedian that's pretty well known in the US, but who is in fact from the UK.
But what about philosohers. Slavoj Zizek is really well known in the US and he's Slovenian. He's published more books with US publishers than he has at home.
University professors are also a great example of a high profession that is ruled by immigrants.