However, it turns out that the US is not the only party involved in international treaties. We can't just pick up the ball and go home mid game, then come back in a year with a new coach and expect everyone to continue playing like nothing happened

The original deal was a difficult achievement on its own. Now, we need to not only repeat that, but also deal with the fact that Iran does not trust us to follow through with our end of the deal. Overcoming that needs good negotiation, and a lot of concessions we did not want to make.

This is why administrations of both parties have historically upheld deals made by the opposing party that they didn't like. Unilaterally breaking deals every 4 years because of who wins an election makes the US a non-credible partner in negotiations. You can't just wave a wand and fix that.