The UN is an attempt to assert global control, true. Unfortunately, the preservation of history and ancient artifacts takes money that people don't want to contribute. Instead of blowing hard at UNESCO, Find us a way to get people to care about the preservation of history and antiquities. Show us the way. That is if you care about old stuff.
Anyway, the UNESCO cannot do more than hand out a shiny plaque perhaps. The Buddhas of Bamiyan were one of those protected sites - look what happened anyway.
http://en.wikipedia.org/wiki/Buddhas_of_Bamiyan
It's also a matter of value for money. UNESCO sucks up billions and hands out glass pearls in return. JMHO.