You forgot chickenshit and batshit. Yes, absolutely. manure will take care of the fertilizer problem to a small extent (small because of the logistical problem of moving all that shit around), but not the pest and weed problem.
American agriculture has hybridized most food plant species to the point that they cannot survive without a massive influx of energy, something on the order of 30 calories of petroleum energy spent for each calorie of food energy produced.
Well, since much of American farmland is becoming desert, don't rule out camels.
See, though, this was my entire point. Barring a return to pre-industrial technology, (i.e. completely organic farming, animal traction and transportation, etc.) which no true red-blooded, teevee watchin', Suburban-drivin', Big Mac munchin' American is ever going to vote for, the United States is going to be remain dependent upon petroleum, the supply of which is steadily decreasing.
It will always be cheaper to invade and rob other countries of their petroleum than to develop viable energy alternatives (not to mention much more stimulating for national morale), and as long as the United States has the military power to do so, then it will continue to do so.
By convincing yourself that you live in the greatest nation ever in the history of mankind, and however bad things might be, well gosh darnit, everything's gonna be O.K. in the end.
Seems to work for most people.