So if I bring a 5K pre paid card to mexico instead of cash for security reasons.... It is subject to confiscation ?
US Debit cards work just fine in Mexico.
None of this is subject to confiscation. You have to report it so they can do a FINCEN 105 form. It is a money tracking regulation. If you don’t declare it and then are caught then it is subject to seizure using your customs declaration as proof. The customs law hasn’t changed, they are changing procedures due to the creation of a new monetary instrument.