If the wife and daughter died, would Miller still go after Ryan?

Do you think he would have? I think no.

When they talk in the desert, miller is aware that they failed to kill Ryan. But Miller believed that he killed Ryan’s wife and daughter. He returns to America only when he hears that Ryan’s daughter and wife survived the crash.

If Ryan were the main target, then Miller would’ve never left America without killing Ryan. His goal was revenge. Sure - he would’ve liked to have killed Ryan. But having Ryan live without his family was ok too.