Why is Trump telling countries do not retaliate to his tariffs?

Like he is the only one that can install tariffs, I can slap you but you can not slap me type thing, I don’t get it.
This isn’t fair trade or free trade it’s simply the world according to Trump.
I can see the us losing a lot of trade before this is over, Canada is already redirecting our oil and LNG to Japan, and China.
Trump stated he didn’t need it so our government found another market.
And taking on China I mean really they have a lot of debt against the us , what if they start calling that debt in?