CORRECTED-Iraq says to close borders with Syria, Iran

Why was this not the plan all along. I have to think that if the US would have stopped people and supplies from coming in from Iran and Syria the problems in Iraq could be 40% to 70% less. I talked to someone who used to be in the military and he said the problem is there is no structure already in place to stop the border flows, and that is why we didn't take care of it right away. If someone invaded the US, they could just take over the border security we already have. Since Iraq has none, securing their borders is a very hard task....
Still, it should have been an early priority to try.