You are a citizen of a state if you are a US citizen and reside in the state, but you may be a citizen of a state, and entitled to vote their, under other circumstances. Generally, I believe (and this is specifically the rule in California) citizens residing outside the US retain citizenship in the State (if any) in which they were last resident, and are eligible to vote more specifically based on their last resident address. (Military voters have different rules, this is general overseas citizens.)

From the US State Department:

>Most U.S. citizens 18 years or older who reside outside the United States are eligible to vote absentee for federal office candidates in U.S. primary and general elections. In addition, some states allow overseas citizens to vote for state and local office candidates and referendums. For information about your state, see the Voting Assistance Guide.

>In some states, U.S. citizens who are 18 years or older and were born abroad but who have never resided in the United States are eligible to vote absentee. Direct your questions about eligibility to local election officials

https://travel.state.gov/content/travel/en/international-tra...