The Royals could have drawn the likes of Blue Square Bet side Luton Town or Oldham Athletic of League One in the round-five draw.
However, McAnuff has insisted that he is pleased to have been paired with the Premier League leaders.
"It's always nice to watch the draw on TV the next day knowing that you are going to be part of it. And what a tie! You look back at the draws that you have watched over the years and remember the teams that you wanted to get and Manchester United at Old Trafford would have been up there every single time," he told Reading's matchday programme.
"For us as players, it is a fantastic prospect - to play the best team in the country and one of the greatest teams in the world. Although it looks like the toughest possible draw, the results at weekend maybe suggest otherwise.
"Not one of those ties would have been a gimmie, you can't take anyone lightly in the FA Cup. Now, we're looking forward to a fantastic game of football up in Manchester and we'll go to Old Trafford and try to get a result."
The tie will be played on Saturday, February 16.