There is no per-country quota for permanent residency, instead there is a worldwide quota of 120,000 employment-based green cards per year, and a law that says "no more than 7% immigrants with the same country of birth" (Note: country of birth, not citizenship).

The only countries that hit this limit are India, China, Philippines, and Mexico. The 120,000 global quota still applies to the rest of the World. Hence, there still are these potential long-ish delays, even if you're not from one of those four countries.