Without exploring the details, I would be surprised if anyone was incarcerated or deported for no other reason than that he was German, either by ancestry or citizenship. Those among your 11,000 would certainly have been scrutinized by security agencies and found to be for some specific reason undesirable.
There were probably 25-50 million people of German ancestry in the USA at the time, so the 11,000 was only one out of several thousand. It cannot be compared in any way at all with the incarceration of every American with a Japanese surname.
“Nobody” is not an unreasonable estimate of a number which is ridiculously small in a huge sample, especially when used for a comparison with nearly everybody in a contrasting sample.
They aren’t euphemisms. There are very substantial legal differences in US law between an authorization for the use of military force and a declaration of war. For example, the Alien Enemy Act, which I mentioned earlier, along with numerous other provisions of law, are only triggered under a declaration of war.
And just to anticipate the next issue, authorizations for force are not new. In fact, Congress passed three of them before passing the first declaration of war against Britain in 1812.
Diplomats may not get to leave right away, but they’re treated a lot better than ordinary foreigners. After the US entered the war the German, Japanese, & Italian legations we put under house arrest at a luxury resort until they could be exchanged with their counterparts (also detained in resorts) via neutral Portuguese intermediaries.