You're right–up to a point: Evil often does seem to have the upper hand in our world; if anything, it's getting worse. Jesus warned that there would be an "increase of wickedness" as the end of this present age approaches (Matthew 24:12). We may be in that time.
But this doesn't mean we shouldn't pray, or that our prayers have no effect–not at all! Yes, the world has much evil in it–but have you ever asked yourself how much worse off the world would be if people stopped praying? I'm convinced God uses our prayers to block Satan's power far more than we realize. In the midst of all the evil that happens in this world, God commands us to "pray in the Spirit on all occasions with all kinds of prayers and requests" (Ephesians 6:18). Jesus told His disciples "that they should always pray and not give up" (Luke 18:1).
On this annual National Day of Prayer, I encourage you and all who are reading this to take time to pray for our nation and our world. Pray that God will restrain the forces of evil, and that justice and compassion will take the place of conflict and hate. Pray too for moral and spiritual revival in our land.
Pray as well today for the leaders of our nation, especially in this election year. The Bible tells us to pray for "all those in authority, that we may live peaceful and quiet lives in all godliness and holiness" (1 Timothy 2:2).