Ah but one must then head south, perhaps with a few stops, IE Italy, North Africa. The circumference of the earth is smaller farther north... etc,etc. Ship routes from the Mediteranian went north to join those comeing from Germany. Rijeka in fact would be about 500 or so miles farther from NYC than Bremen.
Again Bremen was the most common port of departure and had a long history of immigration. Germans were among the first to come to the US.