Although with everything going on in the news no one could blame you for missing it, you should know that US-Mexico-Canada Agreement (USMCA) has been signed, and is now waiting for congressional approval (probably in the next session with the new Congress) to replace NAFTA.
So, the obvious questions are, why change NAFTA, what where it's problems, what are the USMCA's solutions, and will Congress approve it.
First things first, NAFTA has largely been changed for political reasons, namely, Trump just doesn't seem to like it. In fact, many although Economists are (by huge margins) in support of it, many politicians are not, rather baselessly claiming that it lost US jobs.
The funny thing is, for someone decidedly not a fan of NAFTA, Trump has essentially just made "NAFTA 2.0". The only real differences are mandating slightly higher wages and standards for Mexican workers, US access to the Canadian Dairy market, and the closing of the loophole in which Trump placed tariffs on Canada.
Instead of blaming free trade agreements with fewer jobs the US should focus on better equipping the US workforce with more skills, through the education system, and retraining programs. Free trade is good for both countries, and when US workers can't find new jobs it isn't because of a bad trade deal, but poor domestic policy choices.