First off - Turner Cup?
I think you either have the wrong championship or the wrong league in mind. The Turner Cup is presented to the winners of the International Hockey League play-off Championship. The Joseph Turner Memorial Cup is its full title and it was named in memory of Joe Turner.
The USHL and USA Tier I Champions receive the Clark Cup.
The USHL has a history of some wonderful players who have gone through their systems and now play in the NHL: Tyler Arnason, Jason Blake, Scott Clemmensen, Erik Cole, Ty Conklin, Ruslan Fedotenko, Chris and Peter Ferraro, Peter Sejna, Patrick Sharp, Garrett Stafford, to name only a few...
http://www.ushl.com/alumni/
I'd consider that pretty significant considering the fact that the USHL has only been in existence for the past 25 years.
Many of the players in the USHL this past year made commitments to college hockey teams:
http://www.ushl.com/college/index.cfm
And there were 35 players who have played in the USHL which were ranked in the NHL CSS Final Rankings:
http://www.ushl.com/news/20040630nhldraftguide2004.pdf
"Seventeen players with roots in the United States Hockey League (USHL), and six who hope to plant them this season, were selected at the 2004 NHL Entry Draft":
http://www.ushl.com/news/20040627ushl.cfm The most noteable being Blake Wheeler (selected 5th overall) who is protected by the USHL's Green Bay Gamblers for the 2004-2005 season.
The USHL has proved itself to be a very competitive USA Junior hockey league, however it would be hard to compare the USHL to the CHL. I think a game between the two leagues would be fun, but I think if they were to play each other, the only fair way to have a competitive game would be to have "All-Star" teams with the leagues top players to play each other, not the league's top team, because in my opinion, Tri-City had the best overall tallent in the USHL this year only to be stopped in the Clark Cup Campionships by Waterloo's unbelievable goalie Kevin Regan.