"Um, it was Guderian, Rommel was on his right flank."
What are you saying- that Rommel didn't cross the Ardennes and the Meuse in 1940? He did, as did Guderian.
"And there was plenty between them and Paris."
No there wasn't. Sure, there were forces but not enough to stop the armored spearhead which confronted them. As soon as the French leader heard about the forces which had crossed the Meuse, he called Churchill and told him the Battle for France was over. He knew at that moment that their entire strategic plan had failed.
"They didn't go to Paris, they went to the channel, to cut off the Allied armies in Belgium."
That's true, but at that point the Germans had different ways to finish off France. They chose to trap the BEF and accompanying French forces and then deal with Paris.
"They were also counterattacked heavily by large French and British armor formations, at and just after the point of breakthrough."
Yes, in particular at Arras where the British fought hard and exacted heavy losses on the Germans. But that was the British and French armies which had been sent towards the German feint into Holland defending themselves. Those troops were not between the point of the German breakthrough and Paris. The road to Paris was wide open- the Germans simply chose to deal with the troops along the Atlantic first.
The forces between Guderian and Paris amounted to at least a corps of armor, a full division of which counterattacked the bridgehead before German tanks were even across (they were stopped by German infantry). But he didn't go to Paris, he went to the channel. He still had to fight off multiple armor brigade size counterattacks and did so easily.
The reason they went to the channel is their doctrine was annihilation battle, not striking for deep political or command objectives. Western armor theorists whose doctrines call for the latter consistently overlook this or downplay it. They don't like to admit that the greatest success in the history of maneuver warfare ignored their advice and followed much older principles. Which the Germans had employed since the 19th century and were in no way dependent on tanks etc.
The Germans coming through both Belgium and Holland were hardly a "feint", and succeeded frontally, along with the breakthrough success. Yes the main effort was in the Ardennes, but half the force was the fixing group in the north countries, and they attacked seriously, not as a feint.
The Arras counterattack was not larger than the French ones, it was smaller, the French made at least 3 of similar scale. Nor was it more successful. It was stopped readily by gun front tactics because allied combined arms was nonexistent. Brit doctrine at the time stressed armor acting independently - as its prewar theorists had called for - and that failed completely in practice.
The portion of the Allied armies dealt with in the northern pocket was about half. The French had forces to form new lines in the south and did so. But the odds left by the previous victory, along with the proven ability to break through at will, readily beat the remaining French in a second operation. There was, however, such an operation and serious fighting occurred during it, there were French forces to block the way to Paris, etc.