VW Amaroks are manufactured in Argentina and in Germany. Pickups from either source would face a 25% tariff if imported fully assembled. So it's unlikely that they could be cost-competitive with the Colorado. If VW starts building them in Mexico, however, the tariff is removed.
Another possibility would be to assemble the Amarok in USA from an imported kit, which reduces the tariff to 2.5%. This is the way Mercedes imports the Sprinter, for example.
The same 25% tariff is a major reason why pickups manufactured in Thailand (Toyota, Ford, Mitsubishi, Isuzu and others) won't be appearing in USA any time soon. In 2002, negotiations to produce a free trade agreement started between USA and Thailand. But that was suspended in 2006 after a coup replaced the Thai government.
So it looks like the Colorado will have Toyota Tacoma and Nissan Frontier, both made in USA, as its midsize competitors. Both are older designs, in my opinion needing updates to be competitive with the new Colorado.