I need clarification on this rule as I’m not sure if I’m being to literal…

A power can’t attack a territory controlled by or containing units belonging to a power with which is not at war

Here is my scenario Germany is at war with the United Kingdom (but not the United States) the United States is at war with Italy, if The United States has land units on Britan ( or a bomber in my case) if Germany invades Britan do we ignore the U.S. land unit or bomber like in Sea zones or is Germany unable to attack due to the presence of a U.S unit?

I’ve read this so many times my eyes hurt… I’m taking it as Germany cannot attack … Which I am probably wrong but want to hear it from others before I have to tell the hubby he is right ( as always concerning this game!)