An open response to 
Note: I'm wearing a flame retardant suit right now. Any comments that get personal will be ignored. Please stay objective and impersonal if you want to respond.
The basis of this argument centers around one fact: ideas have a way of going viral and no matter how many times tyrants try to kill them off, they keeps coming back and often stronger.
A number of these viral ideas can be traced directly to the violent birth of the United States. I argue that these ideas helped move humanity CLOSER towards actual freedom from tyranny. Even if you disagree about the results of the United States in present and recent history, you should be able to at least acknowledge that placing these IDEAS OF FREEDOM on the global stage was a NET POSITIVE for humanity.
The Declaration of Independence was a game changer that set the stage for future revolutions and the degradation of the greatest empire of the time, Britain. It showed that defiance of superpowers can be done if the cards are played right. Independence remains an idea that went viral to this day.
The Constitution, while obviously flawed since it was created by man and man can't read the future, was as revolutionary as the Magna Carta, particularly because it actually worked and a nation was borne from it.
Also, "allowing slavery" was part of the three/fifths compromise. The slave owning southern states wanted to count their slaves for the census to determine amount of representatives. The anti-slavery northern states obviously didn't want that because it would further solidify the slavery position (similar to more entitlement programs create more voters now).
The three-fifths compromise was to prevent the entire union from dissolving in the negotiations, while still making a fight down the road possible... which became a major catalyst behind the Civil War. At this point in human history, slavery was as common as owning farm animals. This is no longer the case and it would be rather duplicitous to try and argue that the United States had nothing to do with ending open slavery.
On one hand, you're identifying every flaw that America has, but ignoring the obvious fact that no nation grew as prosperous as quickly as the United States, due in part to the very defiance that you mention. The seeds of that defiance are sewn into the very fabric of the Bill of Rights (another revolutionary document).
Artifacts and ideas sprung from the birth of the United States that strive towards MORE liberty:
- Declaration of Independence
- Bill of Rights
- 2nd Amendment (as a concept of self-preservation and the protection of the rest of the Bill of Rights)
- Establishment of Natural Law and Inalienable Rights as a concept
- Separation of Church and State, as a governmental concept with the Establishment Clause
Now, I wrote this as I was putting on my flame retardant jump suit. Saying anything positive about the United States, regardless of caveats or acknowledgement of problems, is often met by mockery and scorn on Steemit. But I'm still willing to have an objective discussion, provided it doesn't get personal (though that seems to happen every time).