The impact American Teams have on pro cycling.

[Finn84]

Since UCI ProTour was established in 2005, following teams from that level have disbanded:

Credit Agricole
Discovery Channel - even if they won TdF in 2007. Many of the key personnel joined Astana.
Domina Vacanze - Sponsor change, effectively Team Milram took that spot
Fassa Bortolo - no sponsor, Petacchi's team so kind of same story as with HTC-Highroad now.
Gerolsteiner - Schumacher and Kohl being tested positive certainly affected that, many riders joined Milram afterwards.
Liberty Seguros - Operacion Puerto, basically replaced by Astana.
Phonak - Had new sponsor who withdrew after Landis being tested positive
Team Milram
Unibet.com - victim of fight between organizers and UCI, couldn't tide any Grand Tour that year even if they had the license.

 

[Swabian Lass]

As has been pointed out in other places, many of cycling's large teams are funded by rich cycling enthusiasts. This includes Leopard, BMC, and Greenedge. Garmin was funded by a wealthy individual. Other teams that appear to be commercial sponsorship actually rely upon a decision maker in the company who is an enthusiast. For example, Team Radio Shack is the pet project of an enthusiast marketing executive who is willing to waste his company's money on a sport that is centered in a continent where the company has no plans to enter. A business model that requires finding a superfan who will overspend his own or his company's money on a team does not sound healthy nor sustainable to me.

You can add Sky to that list. My understanding is that they come out of a combination of Sky wanting access to the London Olympics and James Murdoch being a cycling fan. I mean, it's really nice for him and all that, having his own, pet team, but it's not a sustainable business model.

 

[Libertine Seguros]

Gerolsteiner - Schumacher and Kohl being tested positive certainly affected that, many riders joined Milram afterwards.

Gerolsteiner were already disbanding before those positives came to light. That's why Bettini retired in a huff at Schumacher being bought in as a replacement for him.