Of course it's better than the alternative and I am sure they are thankful. But a common scenario is, send a family rep, typically the father on the dangerous journey, a person most likely to succeed. This person then in the receiving country applies for permission to get his family over too. By the time everything is done, children may have been without their father for two years. Everyone is getting kind of traumatized from it. I am all for thorough background checks, but at least in my country, they take a long time not because of thorough checks, but because the system is seriously backlogged. Most of the time could be cut if we had more resources allocated to the task. Alas, reality, budgets and stuff gets in the way...

How do you do a background investigation on someone from Syria?

Well, you can check with your foreign intelligence agencies to see if the person is suspected of any malicious behaviour or connections, and if the person has acquaintances already in the US, you can ask them questions.