Why Iraq armed resistance is so successful?

Why Iraq armed resistance is so successful?
At one time Iraq had the fifth largest standing army in the world. But the Americans and their allies had to destroy it along with Iraq infrastructure on behalf of Israel. The large number of special-forces and highly-trained military personnel joined the resistance as they were dismissed from service following the invasion of Iraq. It didn’t take long for the Iraqis to find ways around the heavily-armed American cowboys by introducing the highly-effective IEDs, sophisticated booby traps and hard to stop suicide attacks. The Americans keep talking about how their technology can keep Iraq safe, but the explosives continues unabated, mainly due to the ingenuity of the Iraqi resistance fighters.
Here are some examples:
1.The Americans divided Baghdad with huge concrete blocks. But they didn’t know that the resistance can fill them with C4* and drive them to where they are needed.
2.The American officials travel in Iraq using cars with tinted glass. That was great for the Iraqis to tint the glass of their car bombs.
3.Filling the fuel tank with C4 and carry a jerry can pretending that the fuel pump isn’t working in order to pass a checkpoint.
4.Knowing that the Iraqi police check the luggage truck but not the chassis or under the dashboard; Iraqi workshops are taking cars apart and filling every conceivable space including the tyres with C4.
5.On a number of occasion water tanks, wheat sacks, cement bags and generators were filled with C4.
6.Knowing that families receive special preference in restaurants, many of the suicide attackers brought their families before parking their C4 filled cars.
There are other unsuspected items that are currently been used to frustrate the Americans and their agents in government.
*C4 is a plastic explosive. As with many plastic explosives, the explosive in C4 is RDX (cyclonite or cyclotrimethylene trinitramine), makes up around 91% of C4 by weight. The plasticizer is diethylhexyl or dioctyl sebacate (5.3%) and the binder is usually polyisobutylene (2.1%).Another plasticizer used is dioctyl adipate (DOA). A small amount of SAE 10 non-detergent motor oil (1.6%) is also added.C4 is manufactured by combining the noted ingredients with binder dissolved in a solvent. The solvent is then evaporated and the mixture dried and filtered. The final material is an off-white solid with a feel similar to modelling clay. It has a faint bituminous odour and an astringent taste. The Americans use C4 for demolition charges.