Comment by nerdix
The background checks don't always work because they typically use stolen identities or use the identities of Americans that they've paid. They basically have to in order to pass I-9 verification.
There are also different levels of background checks. For instance, previous employment verification can be time consuming so some companies skip it. Checking references aren't useful because they can be faked (you have to run background checks with employment verification on the references to make sure they are who they say they are).
Yes, it generally don't work. Thats why you will find many F1 student with 8 years of experience.....