The most important thing is to DECLARE anything and everything you are carrying that can be consumed as food. Many items are permitted entry, but generally speaking, meat products or meat-containing products are not allowed to enter the USA by way of private individuals. EVEN if they are in a special package from a duty free shop overseas with a seal of quality or whatever. CBP officers take their job seriously, and have the responsibility for enforcing hundreds of federal laws and state laws governing the movement of people and goods into and out of the USA. These laws can be incredibly complicated, and officers have only a few moments with each traveler to do an assessment. Let's cut them some slack.

To the OP: the officer could have dug out the specific regulation allowing him to seize your beef jerky. But it wouldn't have been worth his time or yours. Regarding the cat, I suspect the reason why they were not concerned was that they knew the transporting airline had done due diligence to be sure that all paperwork was correct and the importation of the cat was carried out properly. (If not, the airline itself could face huge fines from CBP for allowing undocumented animals to be transported to the country. Trust me, the airlines would not have let you board with the cat unless the agents verified that your paperwork was in order!) So, the officers at the port of entry didn't bother with too in-depth of an inspection.