We cannot even say that was a magnanimous gesture: The US government simply did not want to endanger the precarious political balance between places that do and do not have growing seasons long enough to make slavery economically viable. And failed at even that, because political activists from both areas abused popular sovereignty by voting with their feet, leading to the laughable "Bear Republic," Bleeding Kansas and, eventually, a war that killed more Americans than all others COMBINED.

If only we had annexed Canada along with all of Mexico all that AND all this could have been avoided.

In all seriousness, illegal aliens are one thing, but it gets very ugly when native US citizens are treated as equally criminal just because the border crossed THEM 150 years ago.