If you are writing about GATE exams then how can you expect to attract traffic from European or US countries? GATE is an Indian exam and only Indians will search for this topic.
However, Mechanical Engineering is a non-country specific topic and you should be fetching traffic from these countries already on your blog. But if you are not getting traffic from these countries then it can be simply because Indian English is a little different from the English of these countries. So, Google might not be showing your blog as a relevant blog for the visitors of this country. There might be an issue with the English quality too. Just write advanced articles based on Mechanical Engineering and make sure these are in-depth articles of minimum 1000 words with proper English and then you should definitely get traffic from these countries.