To summarize briefly:
Jews from Europe are more closely genetically related to Jews from North Africa than either Jewish population is to the surrounding population.
Jews in the United States and South and Central America demonstrate an unprecedented degree of intermarriage with the surrounding population than any "old world" Jewish population. (I use the term "intermarriage" here not in the religious sense but in the genetic sense. Genes don't care if you converted religiously or in which flavor.)