Can we really call the USA a utopian experiment? Depends on your definition. If a utopia is heaven on Earth, then no, not really, because the Founders were too practical for that. But if a utopia can be called an attempt to create a radically different, vastly better society that attempts to increase happiness for the greatest number of people, then yes, definitely.
That’s not to say that the Founders achieved total success. They were, well, less-than-perfect men, what with slavery, and genocide of the aboriginal population, and treating women like property, and all that. But without that initial utopian dream, put into practice through grimy political compromise, how would the evolution of ideas of freedom and equality have occurred? By making the idea of democracy work, imperfectly at first and certainly still imperfect, they proved it was viable. If it had failed, as it did in France due to their reaching too high (resulting in the Reign of Terror, Napoleon, etc.), it could have discredited the whole notion of democracy as dangerously radical for decades or even centuries, just as the notion of communism is discredited today by the disaster that was the Soviet Union.
John Gray claims that utopia is a nightmare that is doomed to end "in a huge river of human blood," and what with the Khmer Rouge and North Korea and Stalin and so on, he has a lot of supporting evidence on his side. And I think he may be right, in the sense that trying to create a heaven on earth, right now, is going to end up badly. But without that utopian dream and the desire to experiment, how do we improve?
What it takes is a balance of dream and practicality, leavened with a good dose of human compassion. America, at any time, is home to hundreds of small-scale utopian experiments, and the vast majority of them, like hippie communes and Brook Farm, fail due to a lack of practicality. Some survive, like the Amish colonies, but in a way that will keep them limited in scope.
The compassion is needed to avoid the fate of many large-scale totalitarian utopias, such as North Korea. Even successful ones that survive for centuries, such as ancient Sparta, manage to be utopias only by building upon the misery of state-terrorized slaves and ideologically enslaved citizens. This is why that bit about the "pursuit of happiness" is so important.
So, while America is far from perfect and no utopia from most people’s points of view, it is in the constant process of becoming a utopia. That it will never reach that indefinable state is probably a good thing, on the whole, but the dream needs to be held onto in order to keep the process going. As long as we’re on the road to utopia, we’re being true to the spirit of America.
Happy 232nd birthday.