United Nations — It's official. The United States on Tuesday became the 194th member nation of the U.N.'s education, science and culture agency, or UNESCO. It was, of course, a formality, after the agency's board welcomed back the U.S. in late June. On Sunday, Secretary of State Antony Blinken called UNESCO's Director General Audrey Azoulay to let her know the documents needed for entry were signed and delivered. "This is a historic moment," Azoulay tweeted. "Our Organization now has 194 Member States & is moving towards universality." It's a historic moment! So happy to announce that the #UnitedStates has officially…