I agree with many of the comments already made. Given the quick collapse of France IOTL, it is easy to overlook the several ways France could have held on during the actual invasion.
If the Allies had gone with the Scheldt plan instead of the Dyle Plan, they might have held the line in France.
If France had positioned more troops at Sedan, the German breakout may never have occurred.
If Gamelin choose to have better communication at his HQ, he could have responded quicker to the breakout.
If Gamelin had not been sacked when he did, his planned counter offensive might have stabilized the French lines. His replacement, Weygand, came to the same conclusions, but he had initially cancelled Gamelin's plans upon being appointed, a crucial delay.
And that's without earlier PODs that could have reformed French armed forces and replace its inferior doctrine. It was a strange defeat. By most measures, the Allies should have won the Battle of France. It's a perfect example of how crucial mistakes can cause a decisive defeat, and how quickly morale can be crushed.