hi in terms of how much money you make per click, does it matter if the user is in the USA or in China or middle east?
Yes, it is also does matter. If visitors come from USA clicks on your websites ads then you get more money for clicks.
ads are country specific. an advertiser who sells products or services will not sell to the entire world and it is often true that north american traffic pays more than the rest of the world.
usa traffic is best, after that come other english speaking countries like canada, uk and australia (since these are also countries that come loaded with a lot of potential buyers). east europe, far east, africa and latin america normally pay very very low.
yes it matters.it effects your earnings.every visitor view differnet adds on your sites depending upon his region