This stayed in my head and I ended up with a whole different idea

Gunslinger has lent out his horse to a friend

Receives letter about a check he sent to his bank not getting there, says he needs to contact them to deal with it by a certain day, which is the day he's getting the letter

Only has his 2 donkeys to pull him in a cart 100 miles into the city. They've always been fine for trips around town but he's not sure if they have the speed and energy for this

After leaving town, donkeys immediately take wrong turn and stop following instructions

Gunslinger cannot abandon his donkeys and is now stuck with them on a wild adventure to Mexico

Mexican villagers think it's very funny to see this American gunslinger on such a detour

Donkeys are looking for some cactus or something they ate as baby goats in Mexico. Today is their opportunity to travel with their gunslinger as an armed guard to go eat some of that cactus again

They find the cactus pretty early in the movie but it's already way too late for the guy to get to his bank so he's lost like $20 in late fees that was a lot of money back then

The rest of the movie is the trip home

Some Mexican gangsters decide this guy will be easy to rob because he can't even control his donkeys, but the donkeys themselves foil the robbery

The border guards are mad when they get back across the border. The donkeys facilitate an escape

The main character stops and gets drunk at some point because they've had such a stressful day

He falls asleep in the cart and the donkeys take him home instead of to a brothel