Were anti-imperial movements nationalist? Could the anti-imperialists movements be considered as nationalist movements?

Yes, the anti-imperial movements could be considered as nationalist as it was the struggle to form an independent nation-states and were inspired by a sense of collective national unity, forged in confrontation with imperialism. European ideas of nationalism were nowhere replicated, for people everywhere developed their own specific variety of nationalism. But the idea that societies should be organised into ‘nation-states’ came to be accepted as natural and universal.