IMO the USA doesn't have that much "space" it just takes awhile to cross. Land utilization is fairly high and much of unused lands needs constant conservation efforts to maintain wildlife.
I mean, you have tons of space there. You spent much time in more densely populated places? I live in China and there are 5 to 6 x more people here for the same size land area as the US. There is so much less free space. Very, very much less!