A grand but complex question, or pair of questions. Broadly speaking, gothic literature addresses two sets of fears. One are the universal human fears: death, dying, suffering, loss, etc. Another set are more specific to the period in which the gothic emerged, and to the societies generating it. Consider, for example, the relationship between monster and creator in Frankenstein. That is very much shaped by period theories about parenthood, by Shelley's own experience of birth, and by class concerns. Therefore, yes, the American gothic would have some distinct fears. For example, it has different concerns about the past, and about the relationship of city and country, than the European gothic does.