Assalamu Alaykum wa rahamtu Allahi wa barakatuh Based on my knowledge from other fatwas, to obtain a citizenship is halal. I am doubtful it is halal. It requires a yes for the following questions of the application N400 PG 9: http://www.uscis.gov/files/form/n-400.pdf "iF THE LAW REQUIRES IT, AR E YOU WILLING TO RAISE ARMS IN DEFENSE OF us?" Aiding kuffar against Muslims ? Those who were born here would be excused for they had no will I assume. Some would say for cases of necessity. And that's SSI only. JazzakALlahu Kahyr

Alhamdu Lillah

  There is nothing to add more that what AMJA declared in this regard:

 There is no harm in citizenship if it is taken as means of organizing the affairs of the residents outside the lands of Islam and establishing da’wah and founding their institutions. This is so long as its (the citizenship’s) possessor keeps his loyalty to his creed and nation (i.e. Islam and the Muslims), fulfills his covenant with Allaah and His messenger, and he and his family are secure of tribulation in their religion.

 For more details, please refer to the whole declaration in the following link;

http://www.amjaonline.com/en_d_details.php?id=322