While its true a good portion of the world COULD fit into texas (if we all lived in tiny one room houses) But due to how humans ACT there is not enough room.
Sure there we could all cram like crayons into a state but humans cant live that closely together..we simply cant because humans are territorial animals.
The reason its said the world cant handle its population is because of how humans ACT not how much space we take up.
Think about how many times you breath an hour and multiply that by 24 and then by the worlds population.
thats alot of air comming in and it takes alot more green plants to recycle that and they take up more space than people.
Do you eat?
Your alive so I would have to assume you do.
Think about the months or weeks it takes for one bit of fruit to come into being ripe the amount of water siol and nutrients it needs.
Animals most of us eat meat.
Average this you need alot of grain or at least 1/2 acer of grazing per cow thats alot of land that cant be inhabited by humans.
Rain forest are needed just for us to breath.
A large part of our land is needed for crops and animals.
Very little of the space in the U.S.A is wasted
But due to car's . littering, polution in general the land that is wasted is so because its toxic our waters are toxic weeven have lakes were you cant not swim or fish in because of its toxic levels.
Rain water is no longer safe to drink in some places.
The sea is dyeing and its a main staple for much of the worlds food and livlyhood.
Oh the earth has enough room to FIT us alright.
But it dosnt have enough room to support us.
Even if we were to stop polution in its tracks there would still be strip mineing and more wood needed than the earth can grow in a year.
More population would mean more food and more water.
There are to many humans as is if we were to crowd together we would start to not only starve to death but also spread illness as badly as humans did in the dark ages croweded together in huge citys.
If you take a view of national parks as wasted space.
Then I advise you to hold you breath because those are what is giveing us alot of our oxygen today.