After extensively searching the web for a product that would remove acid rain spots on my autoglass, I have found the answer. You can spend some cash on specifically designed products that do this but for a few bucks and a trip to the supermarket you can get a cleaner that will give you a beautifully reconditioned glass surface. The product is called Bar Keeper Friend(BKF). Someone on this forum might have mentioned this also. I use this stuff for my beer brewing equipment. It contains light abrasives and Oxalic acid.
What you do with this stuff is first make a paste out of it. Then dab a wet rag in the paste and begin rubbing the glass in a cross hatch pattern using medium to heavy pressure. Let it sit for a minute and rub it again. Try not to get it on your paint. I would recommended that you do one window at a time and wash the window and the surrounding area as soon as you are done working on it. It does require some elbow grease but this method removed the acid rain spots etched into the glass. It also removed any other foreign particles that were adhered to the glass. My autoglass is like new now.