Frankly if Wakanda existed. Most of Africa would hate there guts

Okay, I'll bite. The neighbors to Wakanda had no idea what was going on inside the country. The Wakandan's didn't have lasers and flying craft during the slave trade but definitely could have defended themselves and others but eventually would have been outnumbered by the rest of the world and not just other countries in Africa.

Now that the world knows of Wakanda how is it any different than Stark handing over his Technology to the USA?

And your comment about Native Americans is Erik's point also.

That's one of the things that makes Black Panther compelling: Wakanda's struggle to balance ancient xenophobia and mysticism, and its desire to avoid colonization, against its need to help exploited people. Even within Wakanda, people fight (often to the death) for control of its resources. T'Challa doesn't want to see the whole world descend into war over vibranium technology, and understands this is one of the more likely likely outcomes of revealing Wakanda's mineral treasure. But ultimately he is convinced that he must do so in order to bring about global change.

Killmonger is a great character, ultimately ruthless and megalomaniacal beyond redemption, but part of his motivation was initially noble: He wanted justice for exploited Blacks. Somewhere along the line his focus became supremacy, even at the cost of millions of lives. But his first (and last) desire was freedom from oppression.

That's one of the themes of the film: that Wakanda has only ever taken care of herself. On one hand, it makes sense. Though technologically advanced, perhaps the Wakandans didn't believe they could defeat the entire onslaught of Europeans. Or, even if they felt they could, then what? Where does the obligation end? Are they simply to play policeman to the African continent? Or are they obligated to share their technology. If they do, what if someone turns it against them? And if they horde the tech, they can't be everywhere at once, so many who could have benefited from their medical or military advancements would still die. Even if they could solve all of those seemingly unsolvable problems, then comes the issue of where to stop? Are they only to help Africans? What about, say, the Americas? Should they help the Indians fend of the Europeans? Should they help the Europeans if they're attacked, or attacking one another? It never ends, and until Killmonger came along, Wakanda had always taken the simple route-- isolation and anonymity.