Travelers are likely to be most familiar with Unesco through its world heritage sites such as the Grand Canyon National Park and Yellowstone National Park in the US.
The US claims it's leaving the organization in protest of UNESCO's anti-Israel bias.
The United States has walked away once before under ex-president Ronald Reagan, who quit UNESCO in 1984 over alleged financial mismanagement and claims of anti-US bias in some of its policies.
The withdrawal, effective December 31, 2018, won't be the first for the United States.
And previous year, Israel suspended cooperation with it after the agency adopted a controversial resolution which made no reference to Jewish ties to a key holy site in Jerusalem.
Since 2011, United States arrears to the organization have reached about $600 million, Ms. Bokova said, but she had told members of Congress repeatedly that immediate payment was not an issue, only American political re-engagement in the organization, which she believes serves many American interests overseas.
The United States will withdraw from the United Nations Educational, Scientific and Cultural Organization (UNESCO).
Prime Minister Benjamin Netanyahu has "instructed the Israeli Foreign Ministry to prepare for Israel to leave UNESCO in parallel with the USA", according to his office.
The US stopped paying dues to the global body in late 2011 after the agency voted to accept a Palestinian bid for full membership and now owes approximately $550 million, a State Department spokesperson said.
A press statement from the State Department says the decision was also based on "the need for fundamental reform in the organization" as well as stacking up bills the USA owes UNESCO.
One of UNESCO's founding nations, the United States has had a rocky relationship with the Paris-based organization over the years.
Many saw the vote to include Palestine as evidence of long-running, ingrained anti-Israel bias within the United Nations, where Israel and its allies are far outnumbered by Arab countries and their supporters. With no funds forthcoming, the US lost its vote in the agency in 2013.
Behind them in the secret ballot was an Egyptian career diplomat, Moushira Khattab, with 13 votes, and Tang Qian of China with five, according to results posted on Unesco's website.
"Today is a new day at the U.N., where there is price to pay for discrimination against Israel", Israel's Ambassador to the United Nations Danny Danon said. France's U.N. ambassador, Francois Delattre, had urged the United States to remain in UNESCO this week, saying the United States "must stay committed to world affairs". The U.S. rejoined it in 2003.
The U.S. told Bokova it intends to stay engaged as a non-member "observer state" on "non-politicized" issues, including the protection of World Heritage sites, advocating for press freedoms and promoting scientific collaboration and education.
Irina Bokova, outgoing UNESCO director general, reacted to the development with "profound regret", calling "universality" key to its mission. "Ideally, it steers it in way that USA interests and UNESCO's mandate will converge".