Completely unavoidable. If you live under the boot of colonialism / imperialism, the most immediate and relevant contradiction to people's lives isn't class, it's nationality and race. When both the indigenous elites and non-elites of a colonized area share in the experience of imperial exploitation, that experience forms the basis of a common national identity that positions itself against the extra-national oppressor; that can elide class differences and be reinforced through pre-existing shared language, religion, customs, past polity inclusion, etc.