Yes, the trailer and the RV are imported as a unit and must remain a unit when crossing the border.
A real complication would arise if you let another person, who doesn't own the trailer, borrow it. They could exit Mexico and probably not have any problems. However, when they returned, the trailer would become part of their vehicle's 'importada temporal'. They would never be able to leave Mexico without the trailer, and neither would your RV. What a 'Catch-22'.
Don't loan your trailer. You'll both fall into a trap.
If you want to help your friend, tow your own trailer to the USA and have it removed from your 'importada'. Get the receipts. Sell the trailer to your friend. Re-import your vehicle without the trailer.
A real complication would arise if you let another person, who doesn't own the trailer, borrow it. They could exit Mexico and probably not have any problems. However, when they returned, the trailer would become part of their vehicle's 'importada temporal'. They would never be able to leave Mexico without the trailer, and neither would your RV. What a 'Catch-22'.
Don't loan your trailer. You'll both fall into a trap.
If you want to help your friend, tow your own trailer to the USA and have it removed from your 'importada'. Get the receipts. Sell the trailer to your friend. Re-import your vehicle without the trailer.
