They only lasted four seasons, but they left their mark on MLS. After winning the Supporters Shield in 2001, they never took the field again. MLS was wild back in the day...
Here is an interesting piece of history about the Fusion and the Supporters Shield. From a 2004 thread about the Shield; Andy "Grow Up" Mead posted - "Sam [Sam Pierron, a KC supporter] first presented the Shield to the LA Galaxy supporters at the Rose Bowl in the pouring rain in the summer of 1999. Since then the holding supporters, with one exception, have presented the Shield to the at the Supporters Summit prior to MLS Cup to the new winners. In 2002, Sam Pierron did the presentation as none of the Miami Fusion supporters made the trip - in fact, they spent much of the summer debating whether to hold the Shield hostage, destroy it, send it to Argentina, etc...." I think it would have been rather funny had the Fusion supporters kidnapped the trophy and taken it down to Argentina for a few years.
Where did the original trophy end up? I remember when the Crew held the trophy in 2005 and the team seized it and put it in the trophy case at CCS.