Made a simple mono amplifier (LM386) circuit, and it stopped working. How can I debug individual components?
Since the speaker works, and you've already tried replacing the LM386, there's not much left.

I'd start with the battery.  A short circuit could do horrible things to a 9V transistor battery.

Next would be to remove the 100µF capacitor connected to pin 7.

After that, remove the 100µF capacitor connected to pin 6.

If it still doesn't work, remove and replace the 1000µF capacitor.

You could try trouble shooting by looking at the output of the amplifier.  Disconnect the speaker, and connect the oscilloscope probe to pin 5 of the LM386.  If you see a signal there that follows the input, then that big capacitor is probably bad.

The circuit is simple, and there's not really much that can break.  The LM386 itself is pretty robust and simple - I can't imagine you've destroyed it.



Typical horrible YouTube video schematic.  No designators for the parts, so we have to try to describe which parts are being discussed instead of calling them by name.  

Also, faded almost to illegibility.  I had to hit it with the GIMP and fix the contrast to be able to read it at all.