About the only difference Vietnam (not talking in the North where they had SAM but we were not supplying CAS to troops on the ground up there either) to 'Gan is manpads. Chimbu has spelt it out better than I re the A1. The groundpounders aircraft of choice in Vietnam was the A1 for the reasons Chimbu states plus they could operate in the valleys below low overcasts where no jet could - at least not the ones available F-5, F-4, F-100. Pilots of choice were the VNAF some of whom had 10,000 hours doing the business I believe. How does a modern jet with all is whiz bang targetting gizmos and smart weaponry deliver aid to troops in CLOSE contact with low ceilings/poor viz. In asking of course there is a limit to any aircrafts ability, just suggesting a jet may not be the optimum tool.
Taken from the AW&ST 21/8/06,
"The Pentagon is currently looking at a dedicated COIN aircraft and as a Rand Corp study put it "Insurgencies are likely to be an enduring feature of the international security enviroment." The US services are jointly developing programs for new aircraft, rather than modifying legacy platforms, to meet needs they say reflect the growing counter insurgency requirements. High flying jets would be at a disadvantage for COIN work, which requires more loiter time, often closer to the ground. Jets are also expensive to operate and maintain, and the Pentagon and Congress are looking for ways to cut costs."
The following is being put up as a contender
http://www.stavatti.com/machete/m_overview.html