I would appreciate your input here. Thanks.
First of all, I would not blame illegal aliens for this one. This virus was first discovered in California in 1962, so it has been around for a while. IIRC, the virus actually originated in Asia--but I cannot find the references that would confirm my recollection.
Since it is an enterovirus (the "EV" part of its name), it spreads through the fecal-oral route. This is a very common mechanism of disease spread among young children who have not yet been taught proper hygiene methods. It also spreads through the respiratory route. Teaching kids basic hygiene, such as washing their hands after going to the restroom and before touching food and to stay away from sneezing, coughing people helps to contain the spread.
Last, most enteroviruses--even polio viruses--cause mild disease. That said, there is more reason to think that EV-D68 is responsible for the flaccid paralysis than to think that Zika causes microcephaly. EV-D68 has, in fact, been isolated from some children who developed flaccid paralysis. While correlation is not causation, there is also the fact that these are closely related viruses. Being closely related means that they share some mechanisms of infection, meaning that the characteristics of polio virus that are responsible for it causing paralysis may be present in EV-D68. I should point out here that polio is a very mild disease in 99.5% of its victims, and that it is only the 0.5% who are severely affected with lifelong problems. In order to find such a small effect, it is necessary to analyze a large number of cases. So far, assuming an effect equivalent to that of polio virus, there have not been enough EV-D68 cases to properly analyse.
I do not know if the polio vaccine would give any cross-protection to the EV-D68 virus. It is possible, given the similarity of the viruses. If so, then a child vaccinated against polio might have protection against EV-D68. Even partial protection can be enough to prevent severe disease.