Google uses localized searches! That gives much more beneficial to the consumers.
For Ex: I am in India. Searching for a keyword "Samsung s6 price".
I want Samsung s6 price in India...This is my need...right? Neither getting India price details If I get the price for U.S or U.K, that will not be the right answer I searched for.
Google's main target is to satisfy the user from any country and place!
So this is why Google made the search rankings different from country to country!
Lets come to the deal...
Rank High on USA?
1. Collect USA business listings/classfieds.. Submit on those websites
2. Search for US related websites (Related to your Niche) then post on those websites - Blog comments/forum posts/guest blogging...etc
3. Analyse the competitor's back-links - Use those websites for your link building campaigns
My advice is to target the specific county not the whole USA. High competitive market - you cannot beat the rest within some days.