There are also areas in which we are not using agricultural land efficiently. Roughly 90% of US grain crops are feed to livestock, but there's a question as to how much of that could translate to food suitable for humans. Much of the grain crops are grown on land which would not make suitable farm produce, so it's not like you can assume you can just take that 90% and give it directly to humans to eat. Still it is a lot of land of which is not being used very efficiently. Then there's the agricultural production of India sustained by glacier outwash... something of which is expected to diminish as global warming progresses. And even though they have over a billion people, there is more than enough food produced to end hunger in that country. The most significant limitations there are not in raw agricultural output, but in bad distribution of food and corruption among social classes. Almost everywhere can be found waste which otherwise could be used more efficiently. I favor the US using high speed rail not so much for passengers, but for simply using electricity. If we could stop using diesel electric trains, then the US no longer is dependent on foreign oil. Electric trains can use coal, which will last longer than oil, nuclear, wind, solar... all can take energy from the grid during off-peak hours. Right there is wasted energy available for the taking. I would favor pursuing renewable energies more, but the rate of supply for new solar thermal plants and wind turbines is outpaced by increasing demand. Or it would simply not be feasible to expect solar and wind to save us at the rate they're going. Nuclear really is the most significant step for the US to take in securing energy independence, but improving on inefficiencies is really the best way to go. Permanent and indefinite benefits.