Come on!
Tim Spear surely did not elect the pic (which is definitely NOT original WWII German, check the helmets, I would guess German re-enactors), you contract an agency, they look for the pic that best meets the proposed message (and this pic does, IMHO), and then this is one of the solutions you get.
The capture phrase did not at all specifically state that "in combat you always want an US SOLDIER covering your back" but more the general take we all ex or current solds from whatever nation can share and subscribe to, i.e. the message essentally tells the truth as we understand it (*I* like the pic, and it has nothing to do specifically with being German, would they be Russian grunts it would be ok all along from my POV and still delivering the same msg with the same significance).
What a sad situation where media and people shoot for all the wrong reasons (like for once stating the truth, e.g.) at a politician who did not even personally chose the pic but was ok on the message (shoot at him where he deserves it! Why here?).
Come on!? Get a grip !!
FWIW,
Rattler
EDIT: Now found the pic (as the thingy gets deleted by this forum even with code tags wrapped around it, here in plain text, and the plain text parts italicalized: http:-double slash-i.ytimg-dot-com/Qegp0UK3xMs-slash-2-dot-jpg), the title states it clearly: “Re-enactors dressed as German soldiers advance towards the enemy. Taken at the War and Peace show 08.”