The USA stopped funding UNESCO when Ronald Reagan withdrew from the organization i.e. UNESCO received z.e.r.o. funding from the USA until GWB put a line-item in the 2002 US budget, and when the USA did rejoin it was presented with a $60million bill for payments-in-arrears.
U.S., allies conduct 20 air strikes in Syria and Iraq against ISIS, says U.S. military (Reuters)
from the article: U.S., EU scramble to delay Palestinian bid to join UNESCO