Your thermal camera is certainly ideal for tracking down overheated components!
Yes, a power supply problem is the first suspect when a unit won't power up.
A computer executes a POST (power on self test). If all is well then you see a startup screen. However it sounds as though it detects a short circuit right off the bat and shuts down immediately.
A USB port is exposed to the world. Easy to become damaged by drawing too much current, or, by abuse from malfunctioning peripherals.
If you're skilled and determined, you might go on to the next diagnostic step: disconnect U3801 U3802, then re-install PU4501.
PU4501 may or may not be ruined, depending on how robust it is. The POST may be sufficiently sensitive so as to shut down in time.