kick over the anthill

just kicking the anthill (hitting it with his boot/foot), to see perhaps the reaction of the ants running in all directions ...

full context would help

Yes, take the literal picture of ants running all over after someone has kicked their anthill, and apply it as a figurative concept to creating a lot of mayhem and havoc.

You may use this when there is an ourward appearance of calm, but someone does this as a way to expose the problems underneath.

It's similar to "opening a can of worms".

PhilipIt's similar to "opening a can of worms".

I thought about that one, but I feel it's more negative. The anthill one is more benign, shows plain curiosity wrt what might happen if you make a move in some circumstance.

I have seen cows tear an anthill apart with their horns. Do they do this to destroy the hill or to eliminate an ant that has crawled into a nostril?

It depends on the mood of the cow at the time. Cows are usually quite friendly, but not overly curious, and probably not smart enough to realize that destroying the ant hill would eliminate the ant up her nose.
Sounds like a worthwhile proposal for a government study. What is the cow actually thinking?

Hi,

The lieral meaning is as stated.

But the expression sounds like a figurative way of saying that he caused a lot of trouble, stirred people up, in a previously tranquil situation.

Clive