Cook spaghetti as directed on package, adding broccoli during last minute of cooking time. Drain; return to saucepan. Cover to keep warm.
Meanwhile, in medium bowl, combine Alfredo sauce and half-and-half; blend well.
Brown ground beef in large skillet over medium-high heat for 5 to 7 minutes or until thoroughly cooked, stirring frequently. Drain.
Reduce heat to medium. Stir sauce mixture, cream cheese and mushrooms into ground beef. Cook an additional 2 to 3 minutes or until cream cheese is melted and mixture is thoroughly heated, stirring frequently.
Stir in cooked spaghetti and broccoli. Cook an additional minute. Sprinkle with Cheddar cheese.