Best Ad Network

I have Game with 100,000 impression daily , 25% from usa ,20% from Russia …
i’m use Admob now , but i’m search for new network better than admob ?

Please suggest me which the best in USA ?

You posted almost no information at all, at least not the important one. You should first post your current eCPM, CTR and how often you show your ads. For USA AdMob usually works great, but it depends what types of ads you’re currently using and the placement.

Admob will always be a safe bet for any app/game.
You could try using networks that specialize in promoting other games and apps specifically, as opposed to a mix of all advertisements.
I’ve used StartApp, AppNext and mobileCore that meet this criteria, all with strong and consistent results.
All three networks have attractive and stable interstitial units with varying formats and layouts that perform well across the board.