Mentch,
out of all modern political experiments, American one seems to be most successful, stable, and least bloody. Compare with French, Russian, Chinese experiences. It may be in part due to relatively benign British rule (that evolved over time to a very similar democracy, after all, without any revolutions) and to remoteness from the centers of violence. Still, given the success, you can’t dismiss their theories as simple hypocrisy to cover up slavery.
I suspect people who dismiss American thinkers not only are trying to build up their own theories, but are also covering up their own lack of education. I measured readability level of various authors last year with kids: recent Presidents come up at 6 to 10th grade level, James Madison – as 38th grade … So, maybe people who refuse to read and engage with those arguments simply may not be able to read them.