We have this technology since 1890, minimum. There is no much difference between a submarine and a spacecraft.
There is a huge difference and the spacecraft part is only to get there. The hard part is maintaining an oxygen atmosphere for years and years after you arrive and there is no way that someone in 1890 could do this without several trials first. As for the primitive technology needed for North America it is true that if you don't care about a high survival rate it is easy to colonize: you try an unknown local flora or fauna and if you drop dead the rest of the tribe know not to eat it again.
That approach does not tend to be a popular one unless you are driven by necessity but there is no denying it works. The same applies to crossing the ocean in a primitive boat: you can do it but the odds of survival and arriving anywhere close to where you intend and not large. So it works but, as has been pointed out, technology tends to make everyday life a lot safer and so makes us more risk adverse.