How much do US/Canada bloggers earn from Google AdSense? Do they earn more than Asian bloggers?

Depends where in Asia. If your traffic is all from Singapore it's not much lower than US ad rates. If traffic is from China, Indonesia, Philippines, etc., expect more than an order of magnitude less revenue than an equivalent site with North American users. Ad click prices are far, far lower in countries with lower GDP.

Adsense earning is all depend on the cpc and traffic. If you have traffic from countries like us/canada then you will earn as comparing to Asian countries. It is simple because in the countries like us/canada people are more aware about their health and they keep searching about the health related stuff all day. We know the instruments related to health are very costly. So when adsense show the ads related to these products we get good cpc. I think you may know adsense show the ads as per the user's browsing history. So if they kept searching on the health or other expensive stuffs they will get only these type of ads when they will see your blog.Don't want to say but in Asian countries people like the free things means they almost buy the things which comes with great discounts. So they always get only low rate ads and when they click on these ads we get less cpc. That is the reason every blogger  loves us/uk/canada traffic. You can also read this article to http://www.bloggingtrendz.com/secure-your-adsense-from-ban/ and if you don't have any account yet then you can follow these steps to http://www.bloggingtrendz.com/get-google-adsense-approval-easily/I hope you got your answer :)

Yes, I have a website having visitors from both Asian and US, and I get much more revenue from US. GDP per head talks.

It can never be the same.The advertiser is willing to pay more for a click in US and Europe that in ASIA. http://www.mlipaushuru.com