This post is inspired by a Javanese Muslim prayer: Rumekso Ing Wengi. It's a prayer which symbolizes each body part with a saint or a deity, with the purpose of granting protection and strength to the person who prays.
I've thought about this question a lot, and as somebody who has done so myself, I would say that assimilating these cultures are like going shopping for your body, mind, and soul. I am born and bred Indonesian, but as I visit different countries, I absorb some aspects of the culture that I like. It's like putting on a piece of garment, an armour, or an accessory. And what I put on never leaves me, even as I leave the country and stay out of touch with the culture itself. After I traveled around, I found myself well-shopped enough that I can design my own ideal fashion of culture with the bits that I have picked up along the way. The ideal is, of course, different from people to people, but mine is:
My wits and business astuteness, Chinese
My confidence, eloquence, and charisma American
My work ethic and humility, Japanese
My taste and manners British
My humor Australian, my friendliness Canadian
My efficiency and pragmatism Singaporean
but most importantly,
My heart and spirituality: Indonesian.
So, two points to be made: Firstly, I get to choose what I put on. I have the freedom to make the best of everything that has been given to me. Secondly, if you see me only based on what I am wearing, I am indeed no longer Indonesian. I am a global citizen. But my heart still is, and this shall not change even when my passport no longer is.