Mistaking the initiation of something as the cause of something is a common mistake. A spark starting a fire in a bin of oily rags is technically the 'cause' but that thinking is clearly short sighted. In reality it was the bad practices that created the environment that was the true culprit. This is an example of the same. I suspect there are constant incursions in and near panama but a layered approach of constant study, monitoring, consistent prevention techniques, etc are what stop a surge in 'unchecked northward migration' from something that happens once or twice and is contained and corrected into something that happens constantly and isn't figured out until this has spread and established itself over thousands of miles. So, yes, the spark was 'northward migration' but the 'unchecked' was because we gave up in being good at this job. We de-funded monitoring and study. We put in place political leaders and not technical experts all because 'expert' opinions aren't important. That is what created the 'unchecked' and why we are here now.

The US far-right is famous for (at least) two things:

1. Mistrust in science, and

2. A habit of hastily strangling government watchdog agencies.

#1 has put all such public-safety programs on the chopping block. #2 is the fatal stroke of the axe.