Not a tax accountant, but while just failing to file is a misdemeanor, if you actually owed money and it can be shown that you willfully attempted to evade paying taxes owed, that's a felony (I.R.C. § 7201).

Now, chances are they don't find out, or if they do you can play innocent and pay a fine. Personally, if I were in this situation I would either file, renounce, or never set foot on US soil.

It’s difficult to renounce and you never know if being in the US may become necessary.

People who renounce their American citizenship do so with the funds to overcome this or because they’re committed to living somewhere else.