Originally, Fiats were to be sold by Fiat dealerships in the US when they made their comeback into the US market. However, due to the current economic climate, Fiat decided to use a dealership system that was already in place to keep costs down. Then they were to be sold under GM's dealerships. Now it looks like they will be sold under Chrysler's dealerships.
Part of the problem that lead to the break up of the GM/Fiat joint venture {design and sales} was that GM wanted to rebrand some of the Fiat cars as Chevys when they went on sale in the US. Fiat only wanted to have their cars badged as Fiat, not rebranded as Chevy as well.
Ironically, now that Fiat owns a big chunk of Chrysler, many Fiats will be sold under the Chrysler, Dodge, and Jeep brand names. The "500" will probably be sold as a Fiat or simply offered as the "500" (without a company name) by Chrysler dealers. But the Punto will be rebranded as a Dodge or Chrysler. The 4-wheel drive Panda SUV will be sold as a Jeep. And the Grande Punto will probably be sold as a Chrysler.