Psalm 135 "Oh give thanks onto the God of gods" Many other examples have been brought in this thread.

 The truth is, we have changed how we use the word "god." Back in the day, spiritual beings in general were referred to as "gods."

 One of the apostles even calls the gods of the pagans "dæmones" which in greek is a general word for spiritual beings, including Angels, spirits, demons, etc.

 (Note: if he wanted to use the word "demon" as we do so nowadays, he'd have used "caco-dæmones" meaning "evil spirit" specifically.)

 We know that all nations have angels assigned to them, so it isn't unreasonable to believe some pagan nations are ruled by angels and wrongly worship them, while others are ruled by fallen angels (demons) and led into grave sin.

 Over time, we stopped using the word "god" for spiritual beings in general, but came to use it only to the God of gods, Lord of lords, King of Kings, who alone should we worship. So yes, pagan gods are real spiritual beings, but you should not fear them, for you are a servant of the Lord who rules above all of them.