How lucky your family is to have the rich experience of more than one culture to embrace and share! It’s hard to balance the reality that fitting in is a child’s number one goal for much of middle childhood so not seeming different in any way becomes a reality for them.
I’d recommend that you listen well to his objections and rather than seeing it as a challenge to his cultural identity, recognize it as a normal drive to fit in. You can embrace your culture in the drip-drip ways of everyday experiences to help him love where he comes from. But right now he is saying ‘Let me not be different than others, OK Mum?’
Coming home to a loving and supportive family will mean that when your child grows out of this vulnerable stage, he will likely have been able to integrate both cultures into his sense of self to form his adult identity.