What isn't a good idea is to have zero control over who and what is coming over the borders. This was likely deliberate --- these people intended to get in no matter what it took --- and it looks like they succeeded --- by crashing into the cars at 100mph plus many were able to run off into the desert and will not be punished in any way.
Naturally I am not in favor of illegal immigration. But there are usually multiple causes to any big disaster and the placing of the spike strip appears to be one of them. I am betting that the families of innocent Americans killed in this accident are wondering if the police could have handled this in another way. I expect the officer who placed the spikes is asking himself the same question. I've had a close relative killed in a car accident and I certainly wanted to know all the reasons why it occurred. The police would not have changed their story if they were sure that their actions were 100% OK. Hopefully some lessons are learned.