The (really) rough rule of thumb for where these headdresses are popular is
Hijab: Roughly used everywhere in some form. Many times a generic word for head covering.
Al-Amira: A hijab found in Arabic countries and those places where Muslims wish to immitate Arab outside influence.
Chador: Required by law in Iran. Traditional in Persian areas.
Niqab: Popular in the Arabian Pennisula. Some use in Pakistan since the 1970s.
Burqa: Eastern Iran, Afghanistan, and Pakistan. Becoming the Islamic fundamentalist dress of choice in Europe.
When I was in Iraq the women wore regular Hijabs in the "hair scarf"-style. The only place I knew where the burqa was worn was in a city of 100,000 called Karmah (roughtly between Fallujah and Baghdad). Karmah turned out to be a primary place for al Qaeda to breed as the city was already Wahabbi (the only city to have a native Wahabbi population). The city still is a launching pad for al Qaeda attacks against Fallujah, Ramadi, and Baghdad.