Word gets out. After a few times that US forces quickly zero in on captured soldiers, someone will put it together. Then they can quickly capture a few soldiers, spirit them out of Iraq (say into Iran), and dissect them to find out where the US soldiers tracking devices are.
Then, figure out how to track the US soldiers themselves. Advantage: BAD GUYS!
They don’t have a problem tracking our troops without electronic bugs. But surely we’re smart enough to design a device that can prevent that anyway.