Yes, alarmists need to chill. The sky is not about to fall  - even if Trump were to make good on today's renewed threat to kill NAFTA. 

First, Trump is very likely bluffing - in the silly belief his threat is likely to cow Canada into knuckling under. 

Secondly, it is doubtful Trump has the legal authority to haul the U.S. out of NAFTA without Congressional approval. (This is presently being argued but the no argument is quite compelling.)

Thirdly, there are powerful interests in the U.S. that would see to it that congressmen would say 'nyet' to Trump.

In the meantime, Herman is right: Canada should prepare for life without NAFTA. Not only is it the prudent thing to do given Trump's threats, but preparing ourselves for that eventually is probably the best preemptive of it ever happening. 

My own guess is NAFTA will outlive Trump's stint in the White House.