Does adsense pay less for non us traffic? I've been directing UK traffic to my site, but will I get less $?
I believe google pay less for non us traffic. Google adwords is the advertising program offering for advertisers. Those non us advertisers may bid less due to currency exchange ratio.
Yes, AdWords advertisers can target their ads based on country. Advertisers generally are willing to pay more for US visitors, and there is less competition for non-US visitors, making the bids lower.
I don't think non-US traffic pays badly by definition. I would imagine that traffic pays well in affluent countries. So Canadian, UK, German and Swedish traffic (for instance) ought to pay very well indeed. Add to that the high Euro and the high British Pound and it's pretty clear there is nothing to worry about.
a lot of adwords advertisers are selling products, and the probability to buy is higher from us visitors
I think your visitor's location is a variable Google's smart pricing system will take into consideration. For example, a US orientated ad will have a lower CPC if clicked by a visitor from the UK. In theory this shouldn't be the case due to geo-targeting but sometimes this may be unavoidable.
from what i know, US traffic is the most paying, means if an amarican clicks the ad u get more, compared to, lets say, someone from china who clicks the same ad. it does matter
I have many websites and observe that websites catering to Asian regions are not making much because there are few good paying ads - mostly cheap hotels' and florists' ads . Those getting good volume of US traffic are making some decent earnings - financial services, insurance coverages, etc.