US is 7 times more competitive than Russia. Here is why.
First of all, congratulations. Russia is not an easy market, it is very competitive, and your success shows you are doing things right.
However the number of downloads required for a game to make it to the top ranking in Russia and the US differ greatly. Of course ranking high means that you get maybe as many paid downloads (through advertising) as organic installs.
But to get to the top to be noticed by the top players you need the following number of daily installs:
Top 10 free, iPhone - sorry, dont have stats for Android: US - 17'161 Russia - 2362
Top 20 free US - 5509 Russia - 1256
Top 50 free US - 2712 Russia- 403
To get there you will have a CPI of $2-$3 probably (of course everyone wants a magic figure of $1,5 but only if your optimisation and traffic sources are perfect). If you have that budget, prepare to spend $34'000 for a few days because your competitors are going to be Candy Crush Saga by King.com, and they have money to keep paying to stay up there.