From what people write here, it seems to be easy money to bet against Russia and Austria 
The vast majority of people bet on emotion and not rationality. They easily bet against countries they don't like, especially if they are going to play against someone they like.
Haha, you are right about that, I still make the same mistake from time to time but try to avoid it. When you are a fan of a team, you will be inclined that they will win everything with ease.
I don't think bookmakers look at the U17, these are completely different teams after all. I suppose to some extend the quotes could be affected by hedging (if a lot of people put money on Team A it might be good to offer a better rate for Team B and a worse rate for Team A) but also by which team is playing in their home country. In fact the latter seems to have a huge influence when looking at the quotes discussed here as home teams have much smaller quotes than away teams. I wonder how big this influence in times of Covid and (at least semi-)empty stadiums is?
From what people write here, it seems to be easy money to bet against Russia and Austria
I agree, bookies don't care about the U17 teams; they have their own team of analysts that analyse all news/stats/... of all the teams and based on that, they make their judgement. They can be wrong sometimes and than you can win with nice odds, but it is up to the player to find them.