Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Reserve about 1/2 cup of pasta water before draining. Drain the pasta and set aside.
While the pasta cooks, slice the hot dog sausages into bite-sized rounds. Heat the olive oil in a large skillet over medium heat. Add the diced onions and sauté for 3-4 minutes until translucent. Add the minced garlic and cook for another 30 seconds until fragrant.
Add the sliced sausages to the skillet and cook until they start to brown, about 5 minutes. Stir in the chili powder and cumin, coating the sausages and onions evenly. Season with salt and pepper to taste.
Pour the can of chili (no beans) into the skillet and stir to combine. Let it simmer for 5 minutes, allowing the flavors to meld. If the mixture looks too thick, add a splash of the reserved pasta water to loosen it up.
Add the cooked pasta directly into the skillet with the chili and sausage mixture. Toss everything together to coat the pasta evenly. Sprinkle the shredded cheddar and mozzarella cheeses over the top. Stir gently until the cheese melts into a gooey, cheesy sauce. If needed, use a little more pasta water to get the perfect creamy consistency.
Remove the skillet from heat. Sprinkle chopped green onions over the top for a fresh, vibrant finish. Serve immediately while hot and cheesy.