I tried "Yran" as the answer for the Allied leaders meeting place. Forgot about Yalta. and I'm not sure how I knew Yerba Buena but I did manage to get it after several guesses.
I knew Yerba Buena because there's an island in the San Francisco Bay that still has that name. One of the bridges in that area (I think the Oakland Bridge) passes through it.
It's not a single random town: not only is it the state capital of Utah, it's also the hometown of the Mormon church, and Salt Lake City's foundation and the Mormons cannot be separated - Brigham Young was the church's leader who founded a city and became governor of the fledgling Utah area. There is also a university (and no doubt lots of other things) named after him, so his name will be used often enough in everyday usage in the USA to make it familiar.
Yeah what fit said. It's part of the foundational lore of the Mormon church. It would be similar to asking who led the Jews out of captivity in Egypt, who built the first Temple in Jerusalem, who the founders of Rome were, who founded Alexandria, or which leader led his followers on hijra to Medina.
I wouldn't call the term "Yankee" exceptionally for New Englanders, as it refers to the states the prohibited slavery. This could refer to other Northern states as well like New York, Pennsylvania, and New Jersey. I mean, look at the baseball team the New York Yankees!
More importantly, 3 countries split off Yugoslavia in 1991, only 1 did in 1992. 1992 is technically right, but I wouldn't suggest that.
Either way, as always with front-page quizzes, good quiz!
"Good Grass" (as in Marijuana)
I thought I had spelling problem and didn't know Huan he was known as yellow river.