Heat water in a medium saucepan to boiling. Remove from the heat and stir in instant mashed potatoes. Mix thoroughly with a fork to moisten all potatoes and let stand 5 minutes. Stir in Cheddar cheese, green onion, and cumin.

Preheat an air fryer to 400 degrees F (200 degrees C).

Wrap tortillas in a damp paper towel and microwave on high until warm, about 20 seconds.

Spread 1 tablespoon potato mixture in the center of a tortilla and fold over to make a taco. Repeat with remaining tortillas.

Working in batches, place tacos in the basket of an air fryer. Spray the tops with cooking spray and cook until crispy, about 5 minutes. Transfer to a serving platter and repeat to cook remaining tacos.