The idea that the US was originally founded "by the people, for the people" is not at all what happened. I guess we could say that the government they created was progressive for its time, at least.
Slaves would not have been a large proportion of the country as a whole--about 20% at their height. While the early US did require landownership for adult free males to vote, the US also had unusually high landownership rates. It's estimated that ~60% of free adult males had the right to vote (contemporary Britain had about 15-20% of free adult males having that same rate). So ultimately you end up with about 25% of the current franchise rate, or somewhere in the mid-high teens after taking into account the existence of children who still cannot vote.
The American government does serve the interests of the American people: the American people who own the bulk of the land and the largest companies.
George Washington was the largest landowner in the colonies when the revolution started.