I'm pretty sure the first couple of attempts at North America colonisation either failed completely or the colonisers were absorbed into native american populations.
The first colony in Australia nearly perished through hunger but was saved by the arrival of a second fleet of ships, but who themselves had suffered the loss of a supply ship in bad weather. It wasn't until the 3rd or 4th fleet of ships that the colony even started to move away from borderline starving.
True that. Colonizing would be risky, but out of a billion or so people you ought to be able to find a few hundred that are competent and willing to take on the risk.
A common strategy for Mars missions is to send the supplies there first. You can land habitats, vehicles, food stores, water-producing machines, power plants (and the return vehicle, if we're not talking about one-way missions), and check on them via radio before your crew ever takes off.
The first colony in Australia nearly perished through hunger but was saved by the arrival of a second fleet of ships, but who themselves had suffered the loss of a supply ship in bad weather. It wasn't until the 3rd or 4th fleet of ships that the colony even started to move away from borderline starving.