They were afraid of large numbers of Jews coming in from (in the case of the St. Louis) Germany. 900 people is a lot of people but it would only be the tip of the iceberg if people were allowed to cross the Atlantic and go into the United States. There was a quota of how many people could come in and the US wanted to keep to the quota system.
The United States (at the time of the St. Louis sailing) was neutral, so they also didn't want to endanger that neutrality.
Some people where for it while other thought that it was a wast of time people back then didn't want Americans to loos people over silly disputes
<span>Geosphere <span>is considered as one of the portions of the Earth's system which
covers the Earth’s interior, minerals and rocks, the different landforms and
the processes that forms the surface of the Earth. It is the external part of
the Earth that constitutes the crust and upper mantle. The geosphere or lithosphere is about 35 mi (55km) thick
beneath the ocean and up to approximately 124 mi (200 km) thick beneath the
continents. </span></span>
(See attached file for more details about geosphere)
