The country of your birth has no bearing on whether you are a native speaker. If, as an infant, a parent communicated to you completely in one language - say English - and if as a toddler you were exposed to that language on TV, with playmates and neighbors, and in your pre-school or kindergarten classes so that you were immersed in the language and interacted with numerous native speakers (so that you heard the minor variations in pronunciation, vocabulary, and grammar) you should be considered a native speaker of that language. The degree to which you were immersed in a language determines whether you are a native speaker.
But here is a fascinating fact - when adults learn a language, that language is found in a separate region of the brain. When children learn language, whether it is one, two, three, or four languages, they are ALL found in the same region of the brain. In other words, a child's brain learns all of the languages as if they were just one language. That is why people growing up in multi-lingual families or countries can shift in mid-sentence from one language to another without hesitation while a lot of adult learners must pause and translate from one language to another in their head.