The DR had to declare war or call itself a neutral zone, the U.S. would have none of that during a World Wide War...Fun fact 2: Germany and Japan and everyone else didn't notice.
Not so fun fact: DR opened border to millions of Jewish refugees, and in classic DR style a fraction of a percent made it in. Of course the Trujillo motivation was something about whitening the population, another classic DR nonsensical mentality, no (good) morality behind it.
The Evian Conference and offer by the DR to host Jewish men and women looking to escape Nazi Germany's death camps, is nothing but a slap in the face of so called world leading countries of the time and today.
Whether Trujillo wanted to marry one or whiten the country, leaves no doubt that others saw them as less than human to be saved by any means.
Trujillo was not the DR, just the seating puppet at the time. Millions or a single half deformed person doesn't matter, but someone was saved. Plenty.
The problem of people not taking the offer was a blatant lie at the time, since no country wanted to provide them safe passage on their waters. Those that could, took the offer and had to pay a hefty price and time to navigate waters where they were unwanted. At the time, the DR was not any better than the backwaters Puerto Rico was. People always want greener pastures and be close to other family links, reason why many elected to leave the country after residing enough time for the war to be over and safe passage into other nations opened wide.
As for your didn't notice: Not true.
As soon as the DR became clear on our stand, U-boats started to penetrate DR waters looking for ships to sink that made the route from the U.S. southeastern ports via PR to Europe.
The DR was in effect able to intercept a boat carrying German uniforms, gear and munitions bound to Mexico/SA in our waters. Trujillo soon created a unit that was making use of the intercepted cargo.
A good amount of luger pistols was included on that haul. Reason why you still can find the odd one in some collector hands here. The ammo for them was a good amount and later on Trujillo had the Cristobal Carbine produced in the country (Model 1) make use of the Luger cartridge.