That was the reason why very few people fleeing the rise of fascism in Europe, especially in Germany, could get to the United States. And there were famous incidents like with the MS Saint Louis, which brought a lot of immigrants, mostly Jewish, from Europe. It reached Cuba, with people expecting to be admitted to the United States from there. But the administration of Franklin D. Roosevelt wouldn't allow them in and they had to go back to Europe where many of them died in concentration camps.