The interception of the Zimmerman telegram and German disregard for the Sussex Pledge.
They were not treated well, they were immigrants looking for a better life in the US and they worked for lower wages which took away jobs from people that had been in the US in many industrial cities
Instead of retreating from West Berlin, however, the U.S. and its allies decided to supply their sectors of the city from the air.
The answer is A Angel Island were thousand of immigrants were processed.
