There is some research in social psychology that has investigated when people dislike a group they belong to. Thus, this research is more general in that it is not limited to nationality, but about any kind of social group.
Usually, people have a tendency for ingroup bias, that is, they prefer their own group over other groups (outgroups). One important theoretical perspective that has guided much research on this phenomenon is Social Identity Theory, which posits that people derive their self-concept from the groups they belong to, and strive for positive distinctiveness from other groups.
Sometimes, however, people have a strong dislike for their own group, e.g., because these groups are stigmatized, because a larger ingroup discriminates a smaller subgroup they belong to, because an ingroup violates important personal moral standards, or when people move to high status positions in disadvantaged groups (for a review, see Becker & Tausch, 2014). This phenomenon has been labeled with different terms such as "ingroup hate", "outgroup favoritism", or "disidentification".
To my knowledge, the most comprehensive account of explicit dislike of ingroups has been proposed by Becker and Tausch (2014), who have developed a scale to capture this phenomenon. They distinguish between different components of disidentification and show that their scale can predict negative emotional and behavioral reactions toward the ingroup. Citing from their abstract:
This research introduces a multi-component model of ingroup disidentification that distinguishes three disidentification components (detachment, dissatisfaction, and dissimilarity). In Studies 1a (N = 168) and 1b (N = 215), the authors developed a measurement scale that assesses these components, and examined alternative factorial structures. Study 2 (N = 115) provides evidence that the disidentification scale performs better at distinguishing between disidentification and nonidentification than an established identification scale. Using additional data from Studies 1b and 2, Studies 3a and 3b examined emotions and behavioral intentions as correlates of disidentification and revealed that the disidentification components predict negative ingroup-directed behavioral intentions (active harm, passive harm, and passive facilitation) and identity concealment over and above measures of identification.
Becker, J. C., & Tausch, N. (2014). When group memberships are negative: The concept, measurement, and behavioral implications of psychological disidentification. Self and Identity, 13(3), 294–321. http://doi.org/10.1080/15298868.2013.819991