ramirocastelao:
We agree. You are likely overthinking the value of nationality/citizenship in the process, especially once you are determined to be an international student (assuming you are applying to US schools?)
You will have ample opportunity in your application to indicate citizenship, current residence, etc. Where you take the GMAT and how you indicate your nationality is of minimal to zero importance. Schools are not going to start linking about citizienship to the spot you take GMAT.
Above all, how you weave in your nationality is going to matter in your essays. If it plays a big role in your overall story and background, you should mention it. If it didn't have much influence in who you are (or where you plan to go post-MBA), then it might look forced to include.
We're happy to discuss further.
https://admissionado.com/free-consultation/