I would be very meaningful in a symbolic sense. Germany and most of Western Europe are used to seeing themselves as close allies of the US since WW2.
With close allies you expect to be able to reach an acceptable level of trust on topics like spying, even though you know both sides are still going to do it at some level.
By not being able to sign this agreement the message for Germans / US relations is "we trust you just like we trust the Chinese". That will likely lead to a weakening of past alliances...