Rome did have a defect when it came to cavalry both historically and during the Second Punic War. The main reason as to why Rome did not have an effective cavalry force IMO was the same as why the Greeks were poor at it. Both the Greek and Italian peninsulas were too rocky to lend itself to the raising of horse.

There were isolated areas where Rome was able to raise some horse but they were no where near as competent as their Numidian counterparts. The Senate did realise this deficiency after Trebia and manned a 4,000 strong cavalry force under Caius Centenius to reinforce Flaminius, but he was too late to help the disaster at Trasimene and was later ambushed and annihilated by Maharbal.

It is possible that the loss of 4,000 cavalry was too much for Rome to replace in the year leading up to Cannae. They still had two large cavalry forces at Cannae but to defeat the awesome force of the Numidians they may have needed to have at least double the opposing forces.

I think that this proves that along with learning how to counter Hannibal's tactics, Scipio Africanus's major impact on the war was to get the Numidians to switch sides for at Zama Hannibal didn't have the superiority in cavalry he had enjoyed at Ticinus, Trebia, Trasimene and Cannae