In regard to the current debate over Syrian immigration to the United States, as we witness mass deportations of refugees from Sweden and destabilization in several European countries, it would be well to consider the teaching of Rabbi Moses Chaim Luzzatto, author of Mesilas Yeshorim (Path of the Upright), 1738:
Learn to differentiate between realistic fears and irrational fears. Similarly, differentiate between true trust in the Almighty and folly.
We have an obligation to guard ourselves from potential harm. Failure to behave in a wise manner and opening oneself to danger is not trust in God, but recklessness. Such a person is behaving contrary to the will of the Creator who wants us to guard ourselves from harm.