This article looks at
immigrants as job creators.
I'll give you another reason that fits both immigrants and refugees: survival of the fittest. These are people who left a marginally okay to downright dangerous situation in search of better opportunities elsewhere. Earth has a LOT of displaced people, voluntary and involuntary. Many of those don't make it very far before getting stuck in a camp where work is banned or getting sunk by somebody's navy who doesn't want them landing. So the ones who make it to far-flung destinations like America tend to be the most persistent and capable ... or the luckiest, which also bodes well in entrepreneurship.
A smart country would be taking advantage of that and engaging their skills as fast as possible. Local-America is not that smart. Terramagne-America is a lot smarter (mostly) hence the Rutledge thread of
Polychrome Heroics.