Liberty to do what? Import low skilled individuals that will be a drain on all of us and then wash their hands of the problem beyond using these people for a heat shield? You have not answered the question of how unrestricted migration squares with individual liberty - at least for those who already live here. Are you saying Libertarians believe in global Libertarianism; where everyone, everywhere, is free to do whatever they want? If so, how do those of us without a program tell Libertarians apart from Anarchists
The logical conclusion of individual liberty is that it transcends governments and boundaries. The problem with that thinking now is that human nature is not compatible with a world with no borders. It's ideological pie-in-the-sky thinking. It will be a very long time before humans ever learn to override the problematic nature which borders currently solve. As long as there are different peoples, whose world views are incompatible, there will be a need for nations and borders. This is a major area where I part ideological company with Libertarians. They're so idealistic about this that they confuse their zeal for practicable policies.