The A Very Harold and Kumar Christmas actor left Hollywood to work in the Obama administration's Office of Public Engagement, but returned to acting earlier this year.
Penn explained that working in politics was a wonderful learning experience.
"It's been really interesting. DC and LA are both company towns... The structures are very similar, but the towns are completely different. There's a little bit of culture shock, I guess," he told The AP.
The star went on to say that his time with the Obama administration helped him realise how much he loves the US.
He commented: "This is going to sound cheesy, but it just gave me, as a person who is a citizen of the United States, a greater appreciation of our democracy, the beauty of the push and the pull of our government and what it means to live in the greatest country in the world."
Penn previously revealed that he's very happy to be making films again.
A Very Harold & Kumar Christmas is now playing in US cinemas and opens on December 9 in the UK.
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Watch the trailer for A Very Harold & Kumar Christmas below: