Hi Peter, I am a naturalized US citizen (via employment sponsored H1B to Green Card route). Prior to obtaining my citizenship I held an F1 visa to complete my PhD, and may have overstayed in the US at the end of my studies (I am not sure, this was 15+ years ago). This was never raised as an issue when I applied for my H1B, Green Card or citizenship, but is it something that could become an issue for me now if I travel as a US citizen and attempt to return to the US? Is there anything I can do proactively to address this if it is likely to be a problem? Thank you.

Almost certainly, even if you did overstay, it's not an issue but for peace of mind, you should speak with an attorney because it sounds like you didn't overstay in a way that would have impacted your H-1B, green card, or citizenship applications. (F-1 students are admitted until D/S - duration of status - so they almost never considered overstays.)

Let's put it this way: if you have a problem, you have the same problem as the First Lady and Elon Musk, both of whom violated/overstayed their initial U.S. visas but are now citizens.

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