for instance shamraz khan saying that he would sue in the US for wrongful imprisonment. Y
Firstly, imprisonment and jail time are two diff things. You put someone in jail when you charge him with something, and then you imprison him when the charges are proven in the court of law.
Even in Pakistan I have seen plenty of cases where people kept in jail, or wrongfully accused have ended up filing counter suits. There was a person who was involved in a massive property fraud in Karachi and was doing jail time along with Zardari for less than an year. He got out as they failed to prove any charges against him and he got about 80 lakh rupees from the Govt after filing a lawsuit against them for being wrongfully accused.