Customs is only barely about checking for prohibited items. It's primarily about collecting the proper revenue for goods. The US isn't very protectionist so cus

Customs is only barely about checking for prohibited items. It's primarily about collecting the proper revenue for goods. The US isn't very protectionist so customs is extremely loose. In Mexico they are far more concerned about collecting revenue from customers of US businesses so the customs is more thorough. Based on my experience importing there's about a 2-3% chance any sort of inspection is done at all and that's generally just cursory to compare with the stated manifest classification. Not a search for contraband.