The only way the whole human species will be united is if the entire planet stands up to two countries: the United States of America and the State of Israel. Most of the world views one or both of these countries as the greatest threat to world peace. After doing so, the world can sort out its problems.
Right now, the idea of humans uniting sounds so fantastic. But if you watch those science fiction movies, humans have but their difficulties behind them and are entering a new era. So why can't that be true in the future in real life. We must have faith in the human race.