"The article says, ". . .the United States already has the most stringent process in the world, involving multiple levels of screening and taking 18 months to two years to complete."

Yes, but that's a combination of a claim (most stringent in the world) with some facts (multiple levels of screening, 18 months).  You're supposed to accept the former if you accept the latter.

But that's a non sequitur.

North Korea? Iran? Israel? Virtually any island nation with restricted space? There are a significant number of nations on this planet with stricter immigration policy than the US. It is by no means the most stringent in the world.  Heck, even enacting a full ban (not just a 90 day ban) on a select nation would put it on a list with about 25 other nations, including Israel.