While green card holders can legally donate money to campaigns if they are residing in the U.S., it is not clear whether green card holders residing abroad, even temporarily, can do so.
While the U.S. does not prohibit dual citizenship, some other countries do. Please check with your home country’s citizenship requirements regarding your eligibility to become a dual citizen. Some countries, such as India, require you to renounce your Indian citizenship after acquiring another country’s citizenship.