Yes, but that's not the point. The point is, if you're very strong, like the USA in this screenshot, you can instantly annex all the small countries in the world just by sending them ultimatums. There are no consequences to this. It's just free conquests. Using ultimatums is comparable to using a cheat code to get free stuff.

deppends on how many provinces, how many population and how many soldiers they can recruit, if they cant recruit more soldiers than u, or even lower, they wouldnt wanna loose the population, so yeah, it deppends if the country that has less province that u, mostly will accept it, if your playing as switzerland and wanna send an ultimatium to france, they will decline