So, you live in a country that's controlled by an authoritarian regime. It's likely you have never seen any other form of government in your life. There are things you're not okay with, but overall, it increased your living standard over time, which you consider a good thing. If you're part of the land population, you might even actively support the regime (out of ignorance or not, doesn't matter). Plus, it acts according to your religion, which is likely to be important to you. Plus, it's good at keeping those foreign countries in check that always liked to interfere with you only for their own benefit, and only to your detriment.
Now, the most powerful country of the world comes along. While relations are not good, you haven't actively threatened them. They're issuing an ultimatum: surrender or die. Literally. They talk about democracy, but maybe you know how they treated the last elected leader you had. Anyway, someone pointing their bombs at you while talking about popular self-determination can only be a liar. So you refuse. So they're starting with carpet bombings of your entire civilian population until you give in.
That's exactly the equivalent of the standard plot of an alien invasion story a la Independence Day, you know, those who like to end with these "America saves the day" attitudes. Ever seen any of these movies end in "you know, let's better accept our new alien overlords"?