And now he's back on the streets of the US for no apparent reason other than Democrats want to allow criminal illegal aliens to remain here.
That is not what's happening with sanctuary cities/states. The federal government enforces immigration laws because immigration is a federal thing. No one is asking states or cities to enforce immigration laws. All ICE does is ask the local police department to hold a criminal illegal alien for 48 hours to give ICE time to send an agent there to arrest them. This is the same courtesy local/state/federal police do for one another all of the time if a person is wanted for crimes committed in another jurisdiction; that is the second jurisdiction isn't asking the original jurisdiction to enforce their laws for the person they have in custody, but rather just hold the suspect for a couple of days until the second jurisdiction can take the suspect into custody and bring the suspect to their jurisdiction to await trial.
Does understanding how this actually works change your opinion at all?
No, but why do we want to be the dumping ground for the world's criminals? Let me put this into perspective for you. Let's say your neighbor's 3 year old son comes onto your property everyday and takes a massive shit on your car, forcing you to clean the massive shit up everyday. Would you say "Eh, either my car or my neigbhor's cars." Or would you ask your neighbor to keep a better eye on their son so he stops taking a massive shit on your car everyday?
We all know you would talk to the neighbor but since that would mean you agree we should be sending illegal aliens back home you are either going to say you would allow the massive shit taker to keep doing his thing on your car everyday or you're just going to avoid answering altogether.