@oopty , since there is no tax treaty between US and Panama, and you being US person residing in the USA , you are taxed on world income. You will have to declare your income from Panama and then if ,and only if , Panama also taxes this income, US will allow foreign tax credit ( for income taxes paid to another taxing authority). Many of the tax treaties, agree to have only one jurisdiction tax local govt. funded incomes.
Hope this answers your query