Except the Marines and/or SEALs do come to save people. Perhaps there are political complications you aren't mentioning. Perhaps you got into trouble in a nation with a halfway-functioning government (so diplomacy trumps men with rifles).

It is provably true the US does send armed forces in to save citizens, and it is obviously true that many other countries simply lack the ability to do so. That isn't a license to be stupid, but it is a differentiator between countries with true power projection capabilities and those who don't have the same.