I am confused regarding what I am supposed to declare when driving from Mexico to the United States, as a US lawful permanent resident and French citizen.
https://www.smartertravel.com/customs-duty-free-guide/, which is for airlines (unsure whether the same applies to entries by land), states:
You’ve been out of the country on a much-deserved vacation. About an hour before your plane lands, the flight attendant hands you a U.S. Customs declaration form. Chances are you purchased a few souvenirs or gifts during your travels—so which ones do you have to declare? The answer: Every item you didn’t have with you when you originally left the United States.
https://www.hg.org/legal-articles/what-do-i-have-to-declare-at-customs-when-entering-the-united-states-31665 states the same:
what items must you declare when entering the United States? In essence, you have to declare any items you purchased and/or are carrying with you upon your return to the United States that you did not have when you left.
I assume that I must also declare any agricultural products and any presence of >10kUSD of cash, regardless of where they come from.
However, a US immigration officer told me during a secondary inspection when I was driving from Mexico to the United States that I should have declared items that I were already in my car when I entered Mexico from the US. When I asked him what specifically I should declare, he mentioned as example that I should have declared my clothes present in my car's trunk as well as my electronics. I was advised that my Global Entry privilege would be revoked if I do the mistake again.
Who's right? The websites or the US immigration officer? If the latter (=meaning that when entering the US from Mexico, I must declare items that I had in my car when I entered Mexico from the US), do I have to declare all items, or just a few types of items?