Does "swear to God" a common phrase in western culture?

Native speaker’s answer
Rebecca
Yes, it is! You use it when you are telling the truth. You can also use it as an exclamation, like in this context, when you say you're going to do an action. Both uses are dramatic and used for emphasis. Ex: I swear to God, I'm going to leave this house. => Exclamation Ex: I sweat to God, Laura, you're driving me insane. => Exclamation Ex: I swear to God, I didn't take your necklace! => Truth Ex: I never went to that restaurant. I swear to God. => Truth