The EU could stand up to the US if they felt it mattered.
Other than defence partnerships the EU is no more dependent on the US than the US is on the EU.
It's a two way street.
Unless you think the US would be happy to walk a way from the largest single market in the world (by GDP).
So the EU has teeth if the US pushed it too far.
It's hard to get the EU to agree on a lot of things but something sufficient to make the EU consider punishing the US would likely be important enough they would agree.