Cook lasagna noodles according to package directions. Drain.
Preheat oven to 350 degrees and spray a 9x13-inch baking dish with cooking spray.
In a medium saucepan, whisk together evaporated milk and ranch seasoning. Bring to a simmer over medium heat. Simmer until thickened some. Remove from heat and stir in the red pepper flakes and cream cheese until melted.
Spread about 2/3 cup of sauce in the bottom of the baking dish.
Arrange 3 lasagna noodles in the pan. Top with half the chicken.
Sprinkle on 1/3 of the bacon bits, green onions, mozzarella cheese, and cheddar cheese.
Drizzle about 1 cup of sauce on top of the cheese.
Repeat with another layer of noodles, all the remaining chicken, half the remaining bacon bits, green onions, mozzarella cheese, cheddar cheese, and 1 cup of sauce.
Top with final layer of noodles. Sprinkle with remaining mozzarella cheese and cheddar cheese. Pour remaining sauce on top. Sprinkle with remaining green onion and bacon bits.
Spray one side of a piece of aluminum foil with cooking spray and place it sprayed side down over the lasagna. Place on a rimmed baking sheet and bake for 20 minutes.
Uncover and bake another 15 minutes. Let sit 10 minutes before slicing.