Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente. Drain well and set aside.

While pasta cooks, heat olive oil in a large skillet or Dutch oven over medium-high heat. Add ground beef and chopped onion. Cook, breaking up the meat with a spoon, until the beef is browned and the onion is softened, about 6-8 minutes. Drain any excess grease.

Add minced garlic, chili powder, cumin, salt, and pepper to the skillet. Cook for 1 minute more, stirring constantly, until fragrant.

Pour in the chicken broth and add the undrained Rotel diced tomatoes and green chilies. Bring to a gentle simmer, scraping up any browned bits from the bottom of the pan. Reduce heat to medium-low.

Stir in the softened cream cheese cubes and milk until the cream cheese is fully melted and the sauce is smooth and creamy.

Add the cooked and drained pasta to the skillet, tossing to coat evenly with the sauce. Stir in the shredded Colby Jack cheese until it is melted and incorporated.

Taste and adjust seasonings if necessary. Serve hot, garnished with fresh cilantro, a dollop of sour cream or Greek yogurt, or crushed tortilla chips, if desired.