Why not US & Coalition forces in Iraq just concentrate seal all borders to prevent smuggled arms in?

This is actually being done by British forces around Basra, and Australian forces in the south, they carry out interdiction and interception missions with quite some success!..The American forces, because of the rigidity of their command and engagement structure appear to incapable of doing this! By the time an American field officer has received approval to engage, the enemy has invariably bolted and the opportunity lost, usually with unnecessary US casualty's!..You have to intercept and destroy the insurgents before they do the deed, not sit back and wait for it to happen!..What has to happen is someone in US politics has to have the '' to get the bungling bumbling political general officers out of it, and replace them with officers with field experience who know how to fight a war like this!..They have to follow what the Brits and the Aussies are doing, or they cant win!