Originally Posted by Demise

Honestly lying that you're an LPR can only bite you in the ass if you say it to a CBP agent while trying to seek entry back into the US. Other than that, there's no penalties in the law for lying about it.

Do not ever lie that you're a USC in ANY context though. That shit will make you inadmissible for life with only something like a U-visa being able to save you.