Ford recommends synthetic blend, for models sold in the USA. However the same Expedition sold in Canada or Mexico, Ford recommends full synthetic. Ford doesn't want cheap US owners, complaining about the high oil change cost. I would always use full syn in the EB and change at least 5000K.
It's actually more about the quality of fuels available in other countries. You would expect fuel in Mexico to be consistent due to PeMex being a state-run refinery. It's pretty much the opposite. You never know what you're getting. In Canada, the weather plays a role in fuel quality. Long-term storage in arctic cold can lead to fuel breaking down.
I work in the auto industry. From NASCAR engines, to modern, high-output 4's, to diesels, to some crazy power levels. I have been involved in many, many discussions about oils. "Oil is oil" is NOT a good policy!! There is an incredible variety of base stocks in use, and an even broader spread of additive packages. I won't get into the discussion any deeper than to say that even Mobil 1 has it's limitations. In anything built in the last 20 years, you're safe using ANY good, name-brand synthetic. If you have anything older than the 80's, DO YOUR RESEARCH!!! The level of zinc and phosphorous in modern synthetics will NOT protect your old flat-tappet cam and your old ring materials.
My '16 Expy gets Amsoil Signature series. Do some research on "Low Speed Pre Ignition" (LSPI) in direct-injected and boosted engines.