I don't think it is advisable to introduce a predator / carnivore that does not naturally occur in a given country nor Continent. North America has a good representation of endemic Carnivora: both jaguars and puma (aka mountain lions) as large predators, with mid range lynx (bobcat), wolverine, wolf as well as 3 bears species (black and brown, ... polar bear as a niche species further North in the Arctic).
Introduction an invasive species (that which introduction on a leopard species would constitute) may also constitute a real threat to local fauna and flora maladapted to a species they would never naturally come across nor be able to compete with. There are a Myriad of examples to cite where invasive non-endemic species after introduction have created all hell and havoc among populations of native species or simply outcompete others.
Further since the leopard does not have any competitors in their niche all hell and havoc may ensue in species that are not or maladapted to the présence of leopards. In the professional circles of biologists, ecologists and zoologists generally invasive species are frowned upon and rightly so.