You can use an ad server such as Google Doubleclick for Publishers (DFP) Google makes DFP available for free for most websites.
To use DFP, you have to change the JavaScript tags that power your ads. You would need to set up your ad slots (inventory) in DFP, and generate new JavaScript code to include on your site. Unlike AdSense, DFP uses a block of code in the head of the page in addition to the code for each ad slot.
By default, DFP shows AdSense ads for every slot. DFP allows targeting by demographics. You could set users from various countries to not see ads, or to see "house ads" that advertise other portions of your own site.
Unfortunately, DFP has a pretty steep learning curve. It is much harder to use than AdSense. It used different terminology for the things that AdSense does.