The term 'the American Left' is as near to being meaningless or nonsensical as any term could really be in politics. It isn't really a force in politics anymore. And it would do well to ask itself why that is.
I guess lyrically they're similar because they're talking about escaping the kind of misery that likes company. 'The Last One Alive ' for me is very simple. It's just about alienation really that causes anger.
