Hi @mimi!
Thanks for reaching out!
If you have a lot of global inventory, you can work with AdMob and Millennial in addition to our MoPub Marketplace - along with Lifestreet & Conversant if they have interstitials.
Most publishers will work with Facebook Audience Network and Gemini if they have native ads.
Additionally, this document gives a good overview of most networks and the regions they focus on.
If you have any additional questions, please contact us at support@mopub.com
Thanks!
Adriana