Is this true? Or just a standup joke?

I think the line references the fact that a good cook takes years of practice. Young women will try, but they don't have all those wonderful failures to back up the knowledge of I now know how to cook. The rest of the bit references how when you're young, women have ideals on what to strive for in a relationship. Most people have a perfect ideal in their head of what their future mate will be like. (I would hope that) Most women as they grow up, realize this is just an ideal. See, when you date at an older age, you see somebody's faults and decide whether or not it's a fault you can live with... Young people generally see a fault, and that ends it. Chris Rock just took this little fact and ran with it.
I'm going to stay away from the foreign women comment. :) Hope I helped.

I am 38 years old. I consider a man to have potential if... 1)sex is good, and frequent... 2) he earns as much as I do, or more... 3)he is a leader

Nothing is absolute... It all depends on the woman. The type of woman that a man attracts, depends on his personality. If he is trash, he will attract trash. If he is classy, he will attract a classy woman... Same goes in reverse...

Foreign women are not so picky hahah.
Where did you get that from?
That's a funny thing with many people: "it's always better in another country"
Believe me.
Dutch people (My mom is dutch so I go to The Netherlands alot) are always like "Yeah american girls are easier and more fun" whilst americans say the same about dutch girls.
People usually tend to blame the place instead of themselves.
The reason that in your experience foreign people are more fun is because if you're on vacation your in a much better mood and this attracts people to you. The same with foreign girls in america: their just their for vacation and want a good f***.