As of today, the United States and Israel have lost their vote at UNESCO. This comes as part of standard procedure at the organization, stripping the vote of any nation that fails to pay its dues for two years. The US and Israel stopped paying dues two years ago in protest against the inclusion of Palestine as a member; the US has legislation (PDF), enacted in the 1990's, specifically preventing federal funding of any UN organization that recognizes Palestine.
I'm sure there's someone out there who wants to be all 'well, good, pull out of the UN entirely because screw the UN'. If you are one of those people, take a seat with the others in favor of this development, and let's go over what this actually, in practicality, means.
The first thing it means is that UNESCO's funding is slashed because the United States is the largest contributor (well, until two years ago, anyway). That, they're already dealing with. UNESCO's highest-profile task, as you've seen here if you're one of the two people who come here that aren't something called Vampirestat, is to maintain the list of World Heritage Sites and to contribute towards their upkeep. The most immediate effect the United States will see there is that two American sites most notably nominated for inclusion, the Alamo and Louisiana's Poverty Point (part of a larger tentative list), will see their odds of being named to the list all but eradicated. And no, being named to the list does not mean the UN takes it over. That rumor is completely idiotic. There are no UN peacekeeping soldiers patrolling the Statue of Liberty. The people that come up with this stuff, honestly.
UNESCO does have other tasks beyond that, though. Their Wikipedia page provides a quick rundown of what else they do, but among other things, they fund the International Council for Science; they fund the Free Software Directory; they do all manner of work promoting education; they run the International Programme for the Development of Communication, which deals with journalism and freedom of opinion and expression; and they and several other UN agencies designate Goodwill Ambassadors, which consists of taking celebrities who are on board with the concept and having them spread the word to the media about projects in need of attention. (UNICEF tends to draw the names you've heard of; the likes of Lionel Messi and Shakira and Orlando Bloom and Selena Gomez. UNESCO's list is here.) Those, among other things, get damaged as well.
The most important thing to take into account, though, is purely pragmatic. You want that vote back. You really, really want that vote back. Far beyond the Alamo and Poverty Point, the United States and Israel are a two-nation voting bloc of outsized power in UN agencies. Israel routinely gets ganged up on by the rest of the world, but American power and influence, as well as a Security Council veto, prevents a lot of votes from going against them. With the United States now out of the way, the other members of UNESCO are now free to vote at their leisure without having to care the slightest bit about what America thinks of it, on not only Israel but anything else the United States has an interest in. Which means a lot more votes, not just the Palestine vote, are about to go against American interests, and there is nothing the United States can do about it until it pays its dues.
UNESCO only deals in cultural matters, granted, but the prospect of a key vote falling silent has come up in higher stakes. In January 1950, in protest over the matter of whether the United Nations would recognize China or Taiwan, the Soviet representative to the Security Council, Jabob Malik (favoring China), walked out. There was, however, another matter on the table that the Soviet Union needed to be there for: namely, North Korea's invasion of South Korea. The Soviets were backing North Korea, even helping draw up their war plans. They naturally would have vetoed any attempt by the Security Council to provide assistance to South Korea. But the Soviets weren't around when, in June, the remaining members of the Security Council voted unanimously to provide that assistance, and thus, the Korean War got properly underway.
And this is a big worry among some members of Congress as well as President Obama, who favor passing a waiver to permit UNESCO funding to continue despite the official ban, and tried without success last year to do so. After all, if you're Palestine, you may very well have figured out the game. All you have to do is show up, just show up and have a seat, and your biggest rival just runs off and leaves you free to operate as you wish. And while the United States, a major world influence, is absent, it leaves other nations with designs on influence to flex their muscles and gain diplomatic ground that the United States, already considered to be in decline in that field, will be hard-pressed to reclaim.
The most immediate worry, from my readings of articles on the matter, is that Palestine will gain recognition at the World Health Organization, which as per current law would force the United States to stop paying dues and subsequently lose representation there as well, crippling their ability to handle outbreaks and reducing the possibility of eradicating diseases they currently have on the run, such as polio and guinea worm, and especially reducing their ability to do so within the United States. More long-term, if Palestine becomes a full member of the UN, the consequences would stack up high and fast. Even if people within the United States may not wish to abide by UN decisions, there are plenty of nations that do. Israel, as you may recall, was a creation of the UN. There's a sizable line of countries that wouldn't hesitate to try and take it back the first chance they get.
That becomes the issue at hand. Israel's global influence depends largely on the United States. But how much global influence is the United States willing to forfeit over this?