This is a chronic disease among Democrats, who tend to talk more about what's wrong with America than what's right. When Ronald Reagan touted "Morning in America" in the 1980s, Dick Gephardt famously countered that it was near midnight "and getting darker all the time." This is ironic and weirdly self-defeating, since the liberal message of national improvement is profoundly more optimistic, and patriotic, than the innate conservative pessimism about the perfectibility of human nature.
Klein's complaint is understandable. Democrats routinely act as though America is on the brink of apocalyptic collapse.
But the problem for them in striking a more optimistic note is two-fold: First, many liberals honestly don't believe in American exceptionalism, and see overt displays of love of country as unsophisticated and rube-like. Exhibit A of this phenomenon? Barack's own definition of patriotism, offered in the wake of his decision to stop wearing an American flag pin, when he characterized "true patriotism" as "speaking out on issues that are of importance to our national security.” In other words, protest=patriotism; objecting to policies is the defining feature of love of country, in his formulation. That's hardly uplifting.
The second difficulty is that it's hard to be upbeat about the state of the country if one's solution -- as with most Democrats -- is more government programs. The American people are not naturally inclined to welcome government intervention, and thus must be convinced that circumstances are so dire that no alternative is viable. That's what's behind Hillary's detours to the "dark side" in her speeches (as reported today by the Washington Post). How better to convince Americans to accept massive state intervention in health care (and elsewhere) than by telling them terrible stories of suffering?
Finally, Klein's right in noting that liberals, more than conservatives, believe in the perfectability of human nature. The problem for the Democrats, however, is that they see government as the vehicle for that perfection, and thus any aspect of communal life (except for cultural envelope-pushing) that isn't controlled by the government is somehow lacking. In contrast, Republicans count on religion (not government) to help humans attain a higher level of perfection. They see America's history of freedom from government intrusion -- and particularly its free-market system -- as ideal vehicles for harnessing natural human impulses (like self interest) to work for the greater good of all without the coercion of government control.