This paranoia against immigration seems unnecessary today. It also seems hypocritical if it comes from people who call themselves "Christians." They, supposedly, have read Jesus comments in the Sermon on the mount. The paranoia is also unnecessary, in part, because immigration to the US has slowed down significantly in the last few years. Do we need to spend billions of dollars and upset our ties with big trading partners, such as Mexico, about this now?
I know, a lifeboat can only hold so many people, but our boat is not on the verge of sinking. Crime and terrorism are scary problems, but many more people die in car accidents and folks haven't stopped driving cars. Reasonable vetting and law enforcement can be used to protect public safety.
I think people are rattled by the problems of our crowded planet. Media coverage brings world news to our homes and there is currently a lot of anxiety, in Europe, over immigration. The US is not currently facing the same situation as Europe.
Also, I would guess that the anticipation is worse than the realization. Europe has taken in a lot of refugees which can be an adjustment, but it also means lots of new talent and commerce for their economies. The anticipation can be worse as, looking on a map, Europe is sandwiched between trouble spots in both the Middle East and Africa. One looks at a world map and thinks, "we can't take in everyone," of course.
Our location and situation, here in USA, is less worrisome than in Europe today. We have had more immigration, in our past. More immigration during the 1990s and early 2000s, from what I can gather. It has been an adjustment, as US population has grown, but more people, doing work in our country, does add to the economy. It's less of an issue today, here in USA. Are we reacting after the fact? Are we wasting money and good will by beefing up the border now?