Two people in country A, one from country B, the other from country C.?
Short answer: Yes. Especially if they dont have any exposure to the others language. Long answer: It depends. If, say, person B knows a little about person Cs native language, or vice versa, maybe they can have easier time understanding each other. Heres a story from my perspective. Im natively Indonesian. One of my friends is American (A), the other is French (F). When theyre talking to each other in Indonesian, I can see them struggling a bit to get the other to understand them through their accents. A cant speak the letters Rs and As very well. F always tries to denasalise any vowel thats followed by an n or m (and fails almost every time). When I talk to any of them, though, I can understand him fairly easily. Their accents are unique and make it a bit hard to listen to what theyre saying, but its much, much easier for me and A or F to understand each other. However, when were having a conversation in Indonesian, and they seem to have too much struggle to communicate, we just gave up entirely and speak in English (surprisingly, F is very fluent in English).