Set Instant Pot to saute. Add the ground beef, garlic and onion and cook until meat is no longer pink; drain, if needed.
Add the spaghetti sauce, diced tomatoes, beef broth, Italian seasoning, fennel seed, brown sugar, seasoned salt, salt and pepper to the pot; mix well. Break the spaghetti noodles in half and place them in the pot, separating them as much as possible with fork tongs and making sure they are completely covered with liquid. Do not stir mixture after this point!
Place the cover on the pot and set timer to 8 minutes on high pressure (pressure cook setting). It will take the IP around 10 minutes to build up pressure before it begins cooking.
When cooking is done, do an immediate quick release.
Remove cover, stir and let sit for 5 minutes before serving. Top with Parmesan cheese, if desired.