It seems that without exception anyone transiting the U.S. must go through both U.S. Customs and Immigration on arrival in the U.S. unless precleared.

This most notably affects pasengers to or from Canada but there are other more obscure examples such as Air Tahiti's PPT-LAX-CDG.

Are there other countries or cities where passengers in transit from country a to b via c must go through immigration and customs and actually "arrive" in country c before proceeding to their destination?

From occasional postings here it really looks like some sort of chart or graph listing would be helpful.

Since 9/11 transiting via the US, even on the same plane/flight has become much more complicated.

More airlines are recognising this problem, notably Air New Zealand who fly AKL-YVR non stop. Soon Aer Lingus will fly DUB-YYZ non-stop, negating the need for Irish passengers to transit the U.S.

It would be helpful to know the best locations for easy connections. Narita seems to be really good and also well organised.