Well, it’s not going to stop “bad guys” from getting into our country because they can just as easily fly elsewhere and get here on a boat or cross a land border. That’s one thing Trump doesn’t seem to notice. It’s also going to ignite terrorism ideations in people who are already here from those countries. It’s definitely going to do so inside those countries. Given the chance to come here eventually or do so now illegally, they’ll train there now and come here soon.
On the upside, the good people in these countries might create a stronger task force to get rid of the people that have ruined everything for them. The 99.9% of people in those countries are getting abused with bigotry and now a temporary cessation on their right to come to the one country that promised to give them a better life, and if they work hard to get rid of the people training to commit terrorist attacks, then their country might be determined to be safe for travel from there to the United States. The benefit to the United States is that their country will be taking care of their own issues rather than having those issues spread to the United States and other countries.
This is also going to affect more broad issues like tourism, trade, education, family, among other issues. At the moment, people worldwide are already saying they don’t want to travel to America because they’re afraid of 1) not being allowed in, 2) police discrimination, or 3) civilians discriminating against them. Therefore, this will prevent more formal ties being created like business ties and educational programs like studies abroad, foreign exchange programs, and student ambassador trips. Certainly, this is already destroying families that have family members abroad who can’t come here.
Frankly, this will help to eliminate bad actors from entering the country, but most of them will still get in. They will come in with false papers, whether purchased at the Venezuelan embassy or elsewhere. They will use weapons that are not detected by metal detectors of bomb-sniffing dogs. All the information needed to ascertain which weapons will work and which papers will work has already been stolen by hackers. Therefore, this will help a little, but it will hurt much more.