First, the strategic goal of starting a war is not destroying the opponent's army. It's a resource grab, or changing the government, or mass genocide, or what have you. Guerrilla fighters aren't going to interfere with that significantly, other than forcing the occupants to invest into local corroborators to keep them at bay. Neither is going a dispersed force. See the aforementioned Second Chechen War as an example, where self-reliant terrorists still struggle to this day, while the war in any conventional sense has ended.
The goals of a war vary, most are turf disputes and natural resources are generally involved. Look at RL China today to see this. They are rattling their sabers at India, Tiawan, Japan, Korea, Vietnam, and the Phillipenes for control of all of the south china sea and its resources. One of the hot spots to watch in the news. Some are religious, some are ideology, some are control issues.
Second, guerrillas don't present a fighting force able to face a conventional military. No man-portable anti-air system is capable of challenging even a modern fighter, much less a bomber (unless, of course, employed at direct approach to its airfield). So unless the guerrillas are willing to always face overwhelming firepower - infantry against tanks, aircraft, artillery and god knows what else - they need the aforementioned incredibly complex machine of the rest of the army. And a good deal of it can't be concealed (at least for long) at all, such as long-range radars, capital ships, etc.
Take a look at FARC, the Mujadeen in Afghanistan, Hezbollah and the various guerrlla groups in the Phillipenes. They have cntinued to survive despite the military of those countries trying to wipe them out. Though in the case of Hezbollah, they eventually became a defacto military force rather than guerrila force.
The point of guerrlla warefare is to make your opponent bleed resources using hit and fade tactics. Ambush a check point here, raid an airbase there, attack a convoy there, blow up/plunder a supply depot, eventually sapping your opponents will to fight or get enough local support and resources that an uprising would happen and escalate things to a civil war or war of "liberation" against foreign oppressors. Sometimes this is successful (Vietnahm vs the Japanese, French and U.S.).
Third, guerrillas can't operate for any significant amount of time unless they're supported by the local population, and any prolonged amount of time unless externally supported. Simply for the lack of food, ammo, medicine and other basic necessities.
True, but I'd further define this as support from somewhere, not necessarily the local populace. FARC was/is in bed with drug cartels, as is the Taliban in Pakistan/Afghanistan, they get support from the drug gangs in return for protection and muscle. Vietnahm got its support from the allies vs the Japanese, and used that against the French, and got Soviet support against the U.S (but also had significant local support).
You can with ease. Modern multiple rocket launchers have their impact zone measured in tens of hectares. We have thermobaric launchers even now, too, so cover's not going to help much. So there's no problem with guaranteed neutralizing any enemy presence in any given area of sane size.
And the bad PR that results from using such weapons in populated areas. Sure you can kill the 10 guerrilla fighters in the village by wiping out the village, but at that point the famlies/relatives of those villagers become more likely to fight against you.
BTW-The US has all those toys available to them, other countries may not have those capabilities. SDBs (250lb bombs), and artillery (155mm or less) are preferred for these things since collateral damage is minimized. The US has also been the most successful at defeating guerilla forces (Indian wars, Civil war, Phillipenes Insurrection, and others), with VIetnahm being the exception rather than the rule.
Sorry for the OT post.....forgot which thread I was in and posted before reading all the replies since then.