I cannot fathom why people, whether they are for immigration or not, cannot seem to understand that this issue is a symptom of the government(s) routinely ignoring our freedom of association and private property rights, the full application of which would create some definitely ethnic enclaves (a lot of people, including white progressives, segregate themselves anyway, regardless of signaling or government edict). Deporting 12 million (or more) immigrants is a sort of rough justice, and to my mind, not a particularly great answer to the problem.
Generally speaking I figure if a citizen wants an immigrant here, there ought to be a way. The candidate for immigration would have the promise of a job here, and some place where they'd stay- and whoever sponsor's their stay here has to be liable for the immigrant's actions. So, there would likely be a few undoubtedly multi-ethnic places too, which is fine with me. The real problem to me is externalizing costs for whatever ethnic arrangement strikes one's fancy- not to mention the imposed costs of bad governance.
Additionally, the machinery of the state has to be changed such that the entry of new voters into America cannot mean the destruction of liberty.
Already, from sea to shining sea, there are cities approaching bankruptcy, just as Detroit has already done. The looming waves of bankruptcy indicate the irresponsible outnumber the responsible, and have long voted in governments that are happy to run up debt and generally behave badly.
These things must be fixed. Removal of the immigrants doesn't get at the root of the problem. We are likely seeing a swing from left to right, but it is not clear that anyone is particularly serious about getting the core principles right. If we don't get the core principles right, we will just end up seeing another swing back to the left, whenever they regroup.