Very difficult, I would have preferred to see more european post war cars.
I will start with same guesses now
1: US
2: US or Italy
5: US or russian
7: continental Europe
8: french
9: US
10: US
12: this one is the toughest carquiz I have ever seen the only detail I can see is the rear window, so I have checked Ford Consul (UK), Ford Capri (Europe), E-Type, 911, I do not believe any of these are correct
13: british
15: US
16: US
17: US
19: italian
21: US
Thank you