This is what Obama calls “home grown” terrorism.
Calling it 'home grown terrorism' is an attempt to misdirect.
The perp was born in the US, but his parents were Islamic and from Afghanistan. They and mosque(s) influenced the perp.
It is irrelevant whether the influence and indoctrination was inspired by the Afghan element or the Islamic element or the birth location. The perp was radicalized, and that made him a terrorist -- whether born in NY or Kabul.
Obama uses 'home grown' in an attempt to place the blame on the US and distance the blame from Islam. That only works in the shell-game, because the 'radicalization' came from Islam (mosques and online) and the Afghan (parents) influence. Look here, but not there.