Can legal actions be taken when the person whose car was repossessed leaves the country?

Certainly, all that is necessary is that service is attempted and you have proof of those attempts. If service is physically unsuccessful, you attempt to service the person by registered, restricted delivery, return receipt mail. If this fails, you have the person served by public notice. Once this is accoumplished, you petition the court for a date, show up, and receive your judgment by default.