^Real stretch. X gets a US ppt. as a baby, then goes abroad and doesn't return and knows nothing about tax liability?

X would have had a 5 year ppt. So, by the time X is 21, he would have had to renew his ppt at least twice. Where has X been living. On what visa status?

If X has never returned, but has been earning money abroad, it's free from US tax liability up to something like 80K, which X probably didn't exceed given X is too dumb to understand tax liability.

Embassies have no responsibility to provide tax advice.

Far fetched scenario in my opinion.

People are trying to avoid paying taxes. Period. If they get caught, yes, there will be pain.....in the US and almost all other countries, many of which tax at a much higher ratel than the US.