This oath is required of those who would seek US Citizenship:
OATH OF ALLEGIANCE TO THE UNITED STATES OF AMERICA
"I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state or sovereignty, of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I will bear arms on behalf of the United States when required by the law; that I will perform noncombatant service in the armed forces of the United States when required by the law; that I will perform work of national importance under civilian direction when required by the law; and that I take this obligation freely without any mental reservation or purpose of evasion; so help me God."
Of course, there is this advice offered on Ask The Imam:
Is it allowed to obtain United States Citizenship so that travelling for deen becomes easier?
They require you to promise to bear arms for the country. The oath of allegiance is as follows: The Oath of Allegiance (see above) If they require or ask you to bear arms against a muslim country, what should be the response. Their laws are against 4 marraige law of Islaam. Does the pledge cause any "Ilhaad" or any such anti-islamic view? Please answer according to Hanafi Fiqh.
Answer 5193 2002-03-14
1. If your intention is solely to facilitate easier travel, you are permitted to obtain US citizenship. Although the oath of allegiance is un-Islamic in nature, it will not be treated as an 'Islamic oath'. Therefore, you are not compelled to execute the oath.
2. If you are called up to bear arms against Muslims, you are not permitted to do so by Islamic law.
3. The pledge does not constitute Ilhaad.
and Allah Ta'ala Knows Best
Mufti Muhammad Kadwa
CHECKED AND APPROVED CORRECT: Mufti Ebrahim Desai
Anyone who is not a citizen in this country can be expelled.