Why hasn't it been subdued?
What makes you think it isn't?
(Rom 13:1) Let everyone be subject to the governing authorities, for there is no authority except that which God has established. The authorities that exist have been established by God.
What does God do with these authorities?
(Rom 13:4) For the one in authority is God’s servant for your good. But if you do wrong, be afraid, for rulers do not bear the sword for no reason. They are God’s servants, agents of wrath to bring punishment on the wrongdoer.
Verse 4 tells us that God uses rulers as His servants and agents of wrath. That sounds like the definition of "subdue" to me.
Maybe you or mysteryboy can explain how "God's wrath" exists during what you guys call "the age of grace"?