Does Goole search differs to each and every OS? Like will it be showing the search result in Windows, Mac & Linux?
I don't think that the SERPs provided differ from OS to OS. However, be aware that I've found that the SERPs provided by toolbars can differ from those provided by the search engines when you go to them directly.
Google generally doesn't alter it's SERPs in different OS. However, Bing & Yahoo usually do that. Although, It depends on country to country. For example in China, which has set certain rules for Search Engine results, Bing & Yahoo wouldn't show you the same results as in USA or any where else. Furthermore, It depends on the kind of site too. SERPs in mobile OS are generally different then the desktop OS.
Your operating system won't have any variation in general search engine results; however, you still have to remember that Google has personalized search and web history that can be used to cater search results to a user; thus being different than standard results.
The results shown by google depends on different location as user is based on USA then it just display the only results which are related to USA first.
Search engines results will remain same for all Operating System. I think we won't surprise if you ask does it matter which browser I am using when it comes to search engine results.