If you need traffic from these countries, it is better to have a server location in any of these countries. Using a web host with a server situated in the USA will get you more traffic from the USA due to the geolocation of the server. Google thinks that the server is mostly intended to serve web pages in the USA, which makes sense.
Another way to get US traffic is by writing for the USA. The logic behind it is simple, people read material intended for their use and traffic flows in.
Submitting your website/blog to directories like Dmoz.com, yahoo, bing, and many more USA based web directories will surely help in getting a lot of organic local traffic. But make sure that your website has content intended for the people in the US.
This helps particularly if you are trying for traffic from a specific country. Advertisements help but you will have to spend money on it. As I told that advertising will be promising but costs you a good sum as they value ads more than any other country.
Comments with or without do-follow links will surely help you with this, as you will get to know what topics are discussed and mostly read by the people of that country. You can get an idea of the current trend in the niche you select. This ultimately increases your efficiency in blogging and traffic too.
Also, change geographic location to the USA/UK in Google webmaster tools. This is a very effective tool that can help Google in communicating with webmasters and webmasters can select the geolocation of the website to which pages are mostly intended. Select geographic location of your website somewhere like the USA or UK and attract more visitors from there. However, if you select a particular country, it means the website is more local than global in the eyes of Google. Now, integrate these tips with Babylon’s sophisticated software for geo-targeted traffic and your problems with a lack of traffic will soon disappear.