The simple answer is that there are more reliant, faster, and easier means for a would-be terrorist to enter the United States than to come as a refugee. Here’s why:
Long wait time
The process to apply for resettlement is not quick by any means. An individual must first be granted refugee status by the United Nations after it is proved that they were forced to leave their own country for reasons of persecution. Being granted refugee status does not happen immediately and many individuals must wait to receive their official paperwork that identifies them as a refugee. Only after receiving refugee status may an individual then begin the process to apply for resettlement. Most refugees wait years to be accepted (or denied) for resettlement to a third country. If they are eventually accepted, they still must go through a detailed vetting process to be admitted into their resettlement country. For the United States, refugee applicants can expect a minimum of 18-24 months to complete the vetting process alone, but oftentimes it is longer.
Low Chance of being selected
Less than 1% of refugees worldwide are chosen for resettlement to a third country. Applying for resettlement in no way guarantees a refugee individual that they will actually be chosen. In fact, most are not. A terrorist would also face the same poor chances of being selected for resettlement.
No Choice of Resettlement Country
Most refugees do not have a choice of which country the will resettle to. (A few exceptions might be if they need a specific type of medical care or if they have family members already living in a certain country. But even then, nothing is guaranteed.) A terrorist who seeks to plan an attack on the United States would have no guarantee of actually being sent to the United States. They could instead be assigned to one of the other 25 nations with resettlement programs.
Stringent Vetting Process
If an individual were to make it through the long selection process and also be assigned to resettle in the United States, it is still highly unlikely that he or she would make it through the vetting process. The vetting process involves much more than just a simple background check. It includes fingerprinting and oftentimes retinal scans, personal interviews, medical checks, and numerous security re-checks. Multiple government agencies and security organizations are involved in the process including the Department of Homeland Security, Department of State, National Counterterrorism Center, FBI, CIA, and Interpol. Throughout the entire process, a refugee must repeat their story over and over again to multiple sources. With each re-telling, the story must match what has been already written in their file.
Given the significant wait time, the complete lack of control over where they will be sent, and the vetting process, it is much faster and simpler for a terrorist to enter the United States on a valid visa or to enter illegally.