If you read anything about the drafting of the constitution and the founding of the United States. You would know that Slavery was an institution of Britain's colonialism. That it was so culturally entrenched in the culture, that the founding fathers decided that it was not the time to tackle the problem of enslavement.
Eventually the topic came up, and it was once again shelved. Not until Douglas Adams reinvigorated the debate.
But to say it wasn't trying to solve a particular class of oppression is just wrong. Many of the founding fathers knew slavery should be dismantled as well.
"Slavery's bad, but we're going to keep our slaves, and by 'we' I don't mean the country, I mean many of us talking about this issue right now personally, and do nothing to solve the problem in the long run."
"Also, we're going to go wipe out a bunch of the indigenous people because fuck them."