Cook spaghetti (1 pound) per box instructions, in well-salted water, just to al dente. Drain.
Add the chopped bacon (8) to a large pot (large enough to accommodate sauce and cooked pasta later) and cook over medium-high heat, until bacon is cooked through and is crispy, about 5 minutes. Transfer cooked bacon, with a slotted spoon, to a paper towel-lined plate.
Drain most of the bacon drippings, leaving just enough to coat the bottom of the pot. Discard drippings or save for another use (I always save mine!).
Brown and crumble ground beef (1 pound) in the pot over medium-high heat until there's no pink left in the beef.
Stir onions (1 medium) and garlic (1 tablespoon) into the meat.
Add Worcestershire sauce (1 tablespoon), Cajun seasoning (1 teaspoon), chili powder (1 tablespoon), oregano (2 teaspoons), cumin (2 teaspoons), sugar (1/4 teaspoon), and 1/4 teaspoon salt.
Pour beer (1/2 cup) into the pot and continue to cook for 5-6 minutes, scraping the bottom of the skillet with a wooden spoon, to loosen any brown bits.
Stir in undrained Rotel (1 can), tomato sauce (1 can), chili beans (1 can), and corn (1 cup). Cook until heat through.
Add cooked and drained pasta while it's still hot. Add cooked bacon to the sauce and toss well to coat the pasta.
Adjust seasonings if needed and serve in shallow bowls. Top with Monterey or pepper jack cheese (8 ounces) and scallions (4). Grate some cheese over the pasta and sprinkle with scallions. Garnish with crisp bacon.