Well, of course if suddenly farms stopped producing (they won't), or the population exploded (it isn't), then suddenly we'd have food scares again. That's not happening now, and it seems unlikely it will happen again.
As for running out of space...no. Just, no. In the U.S.? Run out of space? I don't even know how to make sense of that.
And one quick note--I didn't say capitalism is "wrong," just that it isn't doing a very good job at being an economic system that supports life, though some like its liberty (e.g. those who don't have to worry about food and shelter) and some like how it lets them pursue happiness (e.g. those in a position to pursue it, instead of having to work 3 minimum-wage jobs).
(Though, in fairness, if you read my other comments here, you'd see that I don't have a particularly charitable view of capitalism--like one of those old guys said, useful servant, destructive master, or something like that.)