I actually teach a German course to a group of recognized refugees, including Syrians and Eritreans.
From what I've seen, the ability to handle the culture shock varies wildly from person to person and is strongly correlated with age.
The younger a person is, the better they adapt to the new situation. IMO the two main reasons for this are that younger people are more flexible intellectually, and that a significant number of them (but not all!) have had more exposure to other cultures due to the Internet.
I also get the impression that frustration and language skill are correlated. The ability to learn a new language is obviously also correlated with age and educational history.
Note that there are outliers in all directions, but these are the trends that I observed.
Precisely. Indoctrination literally from the moment you are born is unimaginably hard to undo. Impossible, even.