Your able to work any job you like and are qualified for. Some government jobs required US citizenship to be able to obtain the job, others just required a clean background (FBI clearance ) if the job does required you to be a US citizen it will state this right away in the actual job description or job application! Dont be discouraged by what people say and apply! if your able to work no one can take that right away, if citizenship is required the worse that can happen is that they tell you no!

good luck!