I was running a campaign only on USA with some very competitive keywords paying $2.00 per click and after 1 week I had no click and I could see that my average position is 70.0 for the entire week. So today I decided to run the same campaign in all the world with the difference that I'm biding only $0.50 per click and on first day my average position increased easily up to 8.0 due the entire world is less competitive compare to only USA. So can I assume that now I have a better quality score due to my better CTR and my ads in USA will be better placed now even running the campaign in the entire world?
your quality score will improve overall, but you will probably need to adjust your maximum bid if your current bid is ranking your listing in the 70s. Try $10.00 for you max bid and guage where that positions you. Also, you will want to create additional ads (approx 6). Each ad should relate to the search terms you're targeting, but be slightly different than the others. After you test for a few days remove the least performing ads in terms of CTR in order to maximize overall quality score. Also keep in mind, the higher the position your ads appear (1-5 are ideal) the better your CTR and quality score.