You don't any of this to be fact. How many of these idiot terrorists had just recently taken a trip to areas where ISIS holds power? Answer: Most.
Why do you just make up shit when it is easily refuted with facts? Seriously, it makes you look stupid.
Let's use April 2010 as the founding of ISIS. This is when al-Baghdadi became its leader and it transitioned from an Iraqi insurgent group into an actual regional and then international organization.
Muslim terrorists attacks in the USA since that time (have to say Muslim, as there have been more non-Muslim attacks in this time frame):
Triple murder, Waltham MA, September 2011. Very likely done by Boston bomber Tamerlan Tsarnaev and another Russian Ibragim Todashev.
Neither had ever visited ISIS territory.
Boston Marathon bombing, April 2013. Tamerlan Tsarnaev
did not visit ISIS territory. He visited Russia. Feel free to google what Russia does to Chechen Muslim terrorists.
Moore OK head-chopping, September 2014. The perp was an American black who has
never been overseas.
Garland Texas shooting, May 2015. A shitty attempt at Islamic terror, but still an attack.
Neither shooter ever visited ISIS.
Chattanooga shootings, July 2015. The shooter visited Jordan, a nation which takes no shit from ISIS. Espoused pro-Hamas and pro-AQ sentiments while speaking against ISIS to Muslim friends.
Never visited ISIS.
San Bernardino shooting: The asshole couple
never visited ISIS. The man had visited Saudi Arabia to complete the hajj, the woman was from Pakistan and had lived in Saudi Arabia. Neither nation is controlled by ISIS, and Pakistan is quite anti-ISIS.
Orlando shooting, June 2016. Omar Mateen
never visited ISIS territory. Had visited Saudi Arabia to go to Mecca and Medina, some Muslims are smart enough to visit there outside of the hajj so they are not trampled to death or some other crazy shit. Made a side trip it UAE, which is not under ISIS control.
September 2016 NY and NJ bombings. More amateur hour stuff. The bomber had visited Afghanistan and Pakistan, neither are controlled by ISIS.
Never visited ISIS.
tOSU attack, November 2016. Again, amateur hour. The attacker had never visited ISIS territory. Sought asylum from Somali first in Pakistan and then the US, was a child during his time in Pakistan. Somali has a small ISIS presence, but did not at the time of his living there.
Never visited ISIS territory.
If I missed any, I apologize. Anyway,
none of these terrorists had ever visited ISIS territory. What most of them have in common is radicalization by propaganda, both electronic and in a mosque. There is a diversity in supposed allegiance, from ISIS to Hamas to AQ to Chechen radicalism, but not one has ever been linked to actual membership or participation in any group.