I think the Phillies can retain a competitive advantage in LA player acquisition for an extended period due to their investments in Venezeula, including the academy and keeping it open as long as possible. Sal not only built up an extensive network of contacts, he probably built up a lot of good will by keeping the money flowing during a period of extreme economic distress, and the locals know that they withdrew only because it was too dangerous (kidnappings, etc.) to stay. This extends into Columbia, where many Venezualans have emigrated, and even into Brazil.
Even after the crisis is resolved, the Phillies will have a big head start over most teams in rebuilding their network, and they seem willing to expend the resources to do so. The geography of this area means that it's important to have an extensive local network feeding you lead to scout 14-15 year olds, whereas in the DR, which is much, much smaller area to cover and where almost all 30 teams have had a continual presence, most teams are on even ground.
Remember, this ain't the good old US, where there's an airport and a rental car agency and well paved roads within 100 miles or so of every HS and college.
While everyone can expend the resources to scout the top 20 or so prospects, finding hidden gems requires a lot of legwork to out of the way places.