In a large pot or Dutch oven, brown the ground beef over medium-high heat. Drain off any excess grease.
Stir in the taco seasoning, diced tomatoes (undrained), and tomato sauce. Cook for 2 minutes, stirring occasionally.
Pour in the beef broth and bring to a boil.
Add the broken spaghetti to the pot. Stir to ensure it's submerged in the liquid.
Reduce heat to low, cover, and simmer for 15-20 minutes, or until the spaghetti is tender and most of the liquid has been absorbed, stirring occasionally to prevent sticking.
Serve hot, topped with shredded cheddar cheese.
Notes
Optional toppings include sour cream, chopped cilantro, salsa, or avocado.