A monthslong wave of bomb threats against Jewish institutions in the United States that prompted evacuations, heightened security and fears of rising anti-Semitism gave way to an unexpected twist on Thursday. The person responsible for many of the threats, law enforcement officials said, was half a world away, in Israel, a Jewish teenager. An intensive investigation spanning multiple countries culminated on Thursday in the arrest of the 18-year-old suspect, who holds dual Israeli and American citizenship, and his father. The teenager’s lawyer said he suffered from a brain tumor that could affect his behavior. The surge in threats over the past few months — well over 100 sent to Jewish community centers, schools and museums since the start of the year — coincided with an increase in hate crimes…