Which Countries Allow/Prohibit Dual Citizenship?
Countries Which Allow Dual Citizenship:
Bangladesh, Brazil, Canada, Colombia, Cyprus, Egypt, El Salvador, Federal Republic of Yugoslavia, France, Greece, Hungary, India**, Ireland, Israel, Italy, Jordan, Latvia, Lebanon, Lithuania, Macedonia, Malta, Mexico, New Zealand, Pakistan*, Portugal, Serbia and Montenegro, South Africa*, Spain (only in certain cases), Sweden, Switzerland, Syria, Tonga (only in certain cases), Turkey, United Kingdom, United States of America, Western Samoa.
* Persons retain their former citizenship if they apply to retain it before taking out Australian citizenship.
** Also, India announced in the past that it allow dual citizenship with only OCI/PIO for Indian-origins or spouses/children of Indian citizens/Indian orgins.
Countries Which Prohibit Dual Citizenship:
Austria, Belgium, Brunei, Burma, Chile, China, Denmark, Ecuador, Fiji, Finland, Germany, Iceland, Indonesia, Iran*, Japan, Kenya, Kiribati, Korea, Malaysia, Mauritius, Nepal, Norway, Papua New Guinea, Peru, Philippines, Poland, Romania, Singapore, Solomon Islands, Thailand, Venezuela, Vietnam, Zimbabwe.
* Iran does not recognize dual citizenship but continues to recognize its citizens as Iranian.
* Note that Germany has recently amended its citizenship laws so that in some exceptional circumstances, dual citizenship is now allowed. Consult the German Foreign Office web site for details.
Please note however that laws may change in some countries and we cannot guarantee that this list is completely up to date
Which countries requires visa for US citizens
All informations can be found at:
http://www.passportsandvisas.com/visas/index.asp
http://travel.state.gov/travel/cis_pa_tw/cis/cis_1765.html
http://www.henleyglobal.com/visa_restrictions.htm (good resources)