No, crossing a border is not in and of itself a crime.

Unfortunately that is factually incorrect.

https://www.law.cornell.edu/uscode/text/8/1325

https://elaw.klri.re.kr/eng_mobile/viewer.do?hseq=61640&type...

You can find similar laws for the majority of other first-world countries too.

Yeah I'm pretty sure hiding in a cargo while I cross border to Iran isn't shady at all, seems really a legit way to live life.