This is a very hard question to answer. We do not know why God does things, because we are not God.
 
And we are not really sure that God let there be slaves in the USA, or in many other places in the world. Slavery is still happening in places far away. It is bad people who are doing this. The real question that you are asking, and it is a very important question, is - why does God let bad things happen?
 
I am not sure there is an answer. My best guess is that gave the world to us, and asked us to take care of it, to be nice, to be kind, to be respectful. Part of this plan is that the  world is ours to either maintain, or to destroy. God hopes we do the right thing, and that we fight against those who do the wrong thing. But if the world is ours, then we cannot expect God to interfere every time someone does something wrong.
 
If God gave the world to us, then it is really ours, not God's, and we have to look after it. Of course God cares, and it is very painful to see the bad things that people do, and even more painful to do nothing. But if God interfered, then it would not really be a gift from God to us. God would always be taking back.
 
Think of a parent who tells a child - "you are now mature enough to run your own life. Here is your allowance and do with it as you see fit." But every time the child spends the money on things the parent does not like, the parent interferes, tells the child off, and threatens not to give any more money.
 
You would say, and you would be right, that the parent has not been fair, and has not given the child real freedom. This applies also to God, if God would interfere every time someone does wrong.
 
Even as I send this answer to you, I realize that your question is better than my answer. Because the real truthful answer is - I do not know. Nor does anyone else know. And "I do not know" is a good answer, because we cannot know everything, and admitting that is a good thing.
 
But keep on asking questions.
 
 

That's a very good, but challenging question. Any question that begins with "Why does God..." raises some difficult theological questions. One might even ask if God does indeed allow bad things to happen to good people. Therefore, we can say that God doesn't allow people to be enslaved, but rather that humans are free to choose whether they will feel prejudice toward the "other" and whether they will enslave others. It is certainly a shame that history hasn't taught some people a lesson that slavery is wrong. There are still humans who are enslaved around the world. We believe that this is not what God wants of us and we should work to combat this crime. Indeed, there are human rights groups (including in the Jewish community) that try to end human slavery and human trafficking around the world. This is our role as Jews to be an or lagoyim (a light to the other nations) and to practive tzedek (justice).

 

Rabbi Jason Miller is an entrepreneur, influential speaker, blogger and writer. He writes about the intersection of technology and the Jewish world. He owns a tech company, Access Computer Technology, and a kosher certification agency, Kosher Michigan. Follow him on Facebook and Twitter.

It sounds to me that in your question you are starting with the idea that G-d is making prejudice and causing injustice in the world. Is that what you mean? Is G-d prejudiced? Is G-d unjust? That doesn’t sound right, to me.
 
What if it is not G-d, but people who are responsible? After all, we are told that we are given ‘free will’ – a fancy word for having a choice in how we behave and act. That means we can do bad things, even when we know they are wrong. It wouldn’t change what happened, but maybe it would change how we see it, and help us to make it better to think about it that way.

Anytime you say something about a person or group that is something negative about them because of their beliefs or anything about themselves they can’t change, you are expressing prejudice.
 
But if you are expressing prejudice, then the question is not about G-d!
 
I would say that prejudice is never about G-d. It is about how you or I am choosing to act in that moment.
 
An example: If I have a prejudice against people with freckles, and I make fun of them, or treat them badly, I am acting out of prejudice, and as a bigot. I might be afraid of people with freckles – but I have a choice about whether I will act with prejudice or not – and if I can overcome my prejudice, I might just come to learn that people with freckles are good folks.  

If people are the problem, and people have free will, then mistakes can be made again. There is nothing to prevent me from making the same mistake as someone else made in the past – making the same mistake again is not saying that G-d is responsible for it this time, any more than in the past. If we don’t choose to learn from our history, that is our own choice and fault, not G-d’s. 
 
Finally, you ask if G-d cares. I don’t know if anyone can say for sure, but I certainly believe that G-d does care. We have the Mitzvot (commandments) to help us live godly and good lives. That is a gift to us from G-d, and you don’t usually give gifts unless you care about the person to whom you give them. So I would say yes, G-d does care.