there hadnt been any cases “reported” here since the 1960’s which made it “nearly” extinct, until..... the arrival of the “youths” from central America
That's not true. The strain was first identified here in the 1960s, but there have been cases reported between then and now. It's been rarely reported in the U.S., because it's been rarely reported anywhere:
From a 2012 article in the Journal of General Virology:
Human enterovirus 68 (EV-D68) was first isolated from samples obtained in California in 1962 from four children with pneumonia and bronchiolitis (Schieble et al., 1967). Along with EV-D70, EV-D94 and EV-D-111, EV-D68 is one of four serotypes assigned to HEV-D. Unlike other enteroviruses, EV-D68 is acid-labile and biologically more similar to human rhinoviruses in being mainly associated with respiratory disease; however, until recently, reports of respiratory disease due to EV-D68 were rare (Oberste et al., 2004). Between 1970 and 2005 only 26 clinical isolates of EV-D68 were reported in the USA, representing 0.1% of all clinical EV isolates (Khetsuriani et al., 2006). Over the past 3 years, however, outbreaks in Japan, the Philippines and the Netherlands, as well as several clusters in the USA, have implicated EV-D68 as an emerging respiratory pathogen (Hasegawa et al., 2011; Imamura et al., 2011; Kaida et al., 2011; Meijer et al., 2012; Rahamat-Langendoen et al., 2011; Tokarz et al., 2011; Ikeda et al., 2012; Jacobson et al., 2012). The clinical presentation of EV-D68 infections in these outbreaks has ranged from mild illness to complications requiring hospitalization and, in rare instances, death. In all reports, children represented the majority of symptomatic infections. In several clusters, novel genetic variants were described (Hasegawa et al., 2011; Imamura et al., 2011; Kaida et al., 2011; Meijer et al., 2012; Rahamat-Langendoen et al., 2011; Ikeda et al., 2012; Jacobson et al., 2012).
It's rare--here and elsewhere--but it exists. There is no evidence that it is any more prevalent in Central America than it is here. By all accounts, it is pretty rare all over.
I guess we were wasting time for all those 200 odd years of comprehensively screening/quarantining immigrants for disease before admitting them.