FullyFlapped
You're not comparing like with like. The FAA shelled out $20,000 per aircraft to provide the avionics for the Capstone trial in Alaska. A great deal of the safety improvements will have come from the moving map installations and terrain awareness capabilities avoiding CFIT accidents. It has little to do with ADS-B as such. If you could persuade the European taxpayer to subsidise GA aircraft to the same level as the US taxpayer has done in Alaska, I'm sure you'd see a similar improvement in the stats.
Europe is going down the ADS-B road as well. But while the US is creating a two-tier system by introducing the UAT datalink technology as well as Mode-S/1090ES, Europe will almost certainly follow Australia in combining Mode S and ADS-B in the way most compatible with current equipment. ADS-B can be, in effect, little more than Enhanced Mode S broadcast spontaneously without the interrogation of a ground receiver. Many Mode S transponders, for example the GTX330, are quite capable of meeting ADS-B requirements, even though they may not currently be set up to broadcast the data.