Just an update for those wondering, I recently traveled from the US to Indonesia and no major problems faced.
In the US, TSA told me to get the pc out (like a laptop) in a separate bin. They said any large electronics must be in a separate bin. Other than that I went through easily.
In Japan as a stopover, they didn't care.
In Indonesia, they also didn't care.
So all in all, traveling with a PC in those countries should be a-OK