I recently visited Istanbul as well. Too my surprise, I ate the best burger I had in my lifetime. It was a smash burger joint in Emirgan district. Forgot the name. but remember finding it on google maps. Give it a try if you are passing by.
But the good news is you really do not need anything other that Turkish food because it is just amazing.
For example, try getting proper cantonese dim sum in Paris or Barcelona. I only know 2 places in Paris that are halfway decent after having searched quite a bit. Or try searching for good Zhejiang food (the Hangzhou or ningbo style) in Europe.
And Chinese food in most of the US is bastardized to make it much sweeter and oily to conform to the taste there making it absolutely terrible and far from authentic.