America has never seen much of it.
And America's unlikely to see much of it. But the conservative commentators seem very concerned that the lower classes are losing their respect for and deference to the wealthy, and raising the specter of class warfare. If this economic situation deteriorates sufficiently that serious scapegoating is required, and if it bites hard enough that the 'family values/religious right' agenda loses its appeal the the lower middle class, you could see an interesting repolarization of American politics.
Right now, the suggestion seems to be that increasing the progressivity of the federal income tax structure is tantamount to class warfare on the wealthy. I disagree. All that is on the table right now is modestly undoing the diminuition of rate progressivity that has been the pattern for the last quarter of a century.
Class warfare would be using the tax code to destroy certain ways of life. For example, the tax code currently imposes a confiscatory excise tax on the proceeds from the sale of machine guns. If you amended the tax code to impose a confiscatory excise tax on any income derived from investment of the proceeds of a bonus paid in the last X years by an institution that subsequently received TARP funding, that might be construed as class warfare. Particularly if you did it in such a way, with presumptions of attribution, etc., that essentially confiscated the future income of any bonus recipient.
Warnings against class warfare will probably cease when it dawns on those making them that right now the idea has a certain amount of political appeal. Politically, that appeal appears to be growing. Candidly, it's about time that the pendulum swing on the income distribution front.