I'm not thrilled about what current US administration is doing when it comes to international NGOs. UNESCO is one example.
However, there's also another problem: various UN bodies became tools for international politics instead of doing what they were originally designed to do. It's another example of good will easily subverted by malicious actors to serve shady political goals.
These international organizations need restructuring that would introduce some sort of a watchdog that would make sure these organizations don't overstep their aria of responsibility. Similarly to how constitutional democracies usually have separation of power and multiple branches of government that are supposed to counterbalance each other.
My layman understanding of the reason for UNESCO existence is the preservation of cultural heritage. This shouldn't be political. This should be based on historical or archeological knowledge as well as arts. However, UNESCO as well as eg. UNICEF and other similar orgs shamelessly engage in political activism that has nothing to do with conservation efforts. The officers of these organizations haven't been elected to represent political wishes of their constituents. They bare no responsibility for the effects of political propaganda they are spreading, but it's impossible to prevent them from doing something they shouldn't be doing by all accounts.
Bad political actors found a way to subvert and misuse organizations that were intended for a good cause. We need to figure out a way to fight this subversion. Defunding is both too late, and comes at a cost of not having an organization that cares about preservation of historical heritage or the rights of children etc.