How long can US citizens stay abroad?
How long can US citizens stay abroad? Absences of more than 365 consecutive days You must apply for a re-entry permit (Form I-131) before you leave the United States, or your permanent residence status will be considered abandoned. A re-entry permit enables you to be abroad for up to two years.
What is the penalty for US citizens entering leaving the US on a foreign passport?
Thus, the penalty is the possibility of denied or delayed entry into the US, as well as the associated costs (e.g. missing connecting flights or meetings).