“It’s more useful, then, to focus on how easily the Islamic State can strike Europe in comparison to the United States. And here the contrast is clear. Over 5,000 Europeans have gone to fight in Iraq and Syria; less than 200 Americans have joined the struggle. Europe also shares a land border with Iraq and Syria via Turkey and is logistically far more accessible for Islamic State fighters to go back and forth, while the United States is protected by two great oceans. Even putting foreign fighters and simple geography aside, Muslim communities in Europe have more radicalized individuals who stay in Europe, and thus a greater native pool of recruits for lone wolf and other attacks.”
Source: Europe vs. America: Comparing the Terrorism Threat – Lawfare
