268,820 sq mi * (5280 ft) ^2 / 7,000,000,000 = 1070 sq ft/person
A family of 4 could fit on 4280 sq ft (65x66'), so yes. It wouldn't sustain them, but yeah, the houses would fit.
As far as the depopulation goes, here is an example quote, from Paul Watson, leader of Sea Shepherd Conversation Society, which is featured on the Animal Planet TV show Whale Wars:
I was once severely criticized for describing human beings as being the
"AIDS of the Earth." I make no apologies for that statement. Our viral
like behaviour can be terminal both to the present biosphere and
ourselves. We are both the pathogen and the vector. But we also have
the capability of being the anti-virus if only we can recognize the
symptoms and address the disease with effective measures of control.
...
We should not be living in human communities that enclose tiny
preserved ecosystems within them. Human communities should be
maintained in small population enclaves within linked wilderness
ecosystems. No human community should be larger than 20,000 people and
separated from other communities by wilderness areas. Communication
systems can link the communities.
...
We need to radically and intelligently reduce human populations to
fewer than one billion. We need to eliminate nationalism and tribalism
and become Earthlings.
...
Sea transportation should be by sail. (Funny that he says this, as his Sea Shepherd boat, which is very large, is not operated by sail.)
...
Who should have children? Those who are responsible and completely
dedicated to the responsibility which is actually a very small
percentage of humans.
...
Curing a body of cancer requires radical and invasive therapy, and
therefore, curing the biosphere of the human virus will also require a
radical and invasive approach.
Of course, I think people should be reasonable and respect the fact that we have limited resources, but many "green" activists are zealots and go too far overboard. Watson is a great example of this.
I also think people who hate to see animals owned by humans are pretty crazy. Man and animal have been joined at the hip for tens of thousands of years, and there is nothing wrong with it. Locking an animal up in a tiny cage for long periods of time, for their entire life is obviously not good, but there is nothing wrong with a house cat or a dog that lives in the backyard, so long as you afford it the ability to have a respectable existence.