Agreed with you on the first two, which is why I think people can reasonably argue that we should leave the place, as we have no set idea on whether the resources will be worth it in the long run.
Additionally, there's a chance that all these fire ants will stop bothering us or lessen their attacks if we remove ourselves from the equation, instead turning on each other (Not guaranteed, to be sure, but a chance.)
Finally, if we took even half of the money that was being spent overseas, and instead invested it in thinktanks and better forms of security, we might be able to protect ourselves better. Airports, for instance, still are designed horribly in regards to safety measures.