It would be SO easy for 200 bad guys, out of the millions who have walked across our border, to gather and coordinate an attack on a small Texas town. With the same level of ruthlessness as the Israel attacks, total devastation and 100s of deaths could be achieved in a single day. This is not SHTF doom and gloom. It is possible. Israel is proof it is possible. Of course 911 is also proof it can happen. Our leaders don't care about who is coming into our country and the surely don't care about any small podunk Texas town. They DO care about disarming the small podunk Texas town though.
And our government will publicly act TOTALLY surprised!!
What happened in Israel is literally nothing in scale compared to what could relatively easily be done here by a hand-full of coordinated attackers. We are ALL on literal life support in the form of the electrical grid due to the inability to produce, preserve, and distribute food without electricity. This is by far the biggest existential threat to the US.
There are a couple of very vulnerable areas, and due to government incompetence, the grid isn't hardened against either. One is an EMP attack via a simple nuclear weapon being detonated a couple hundred miles above the US. This has been studied in detail by the US EMP Commission. The EMP Commission was created by Congress in 2001. The commission is formally known as the Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack. The Commission brought together notable scientists and technologists to compile several reports. In 2008, the EMP Commission released the “Critical National Infrastructures Report”. This report describes the likely consequences of a nuclear EMP on civilian infrastructure.
The findings and conclusions of this report to Congress are more scary than any localized event could ever be (except for those few people caught up in the localized event, of course). CLIFF'S NOTES: The result of a strong EMP attack (such as a relatively simple, easy to build but harder to deliver nuclear weapon being exploded 200 miles above the Central US would be 90% of the US population dead within one year. The deaths would be due to the fact that the electrical grid and essentially everything that uses electricity to function (vehicles, refineries, food production and storage, transportation, etc., etc.) will never work again unless/until many of the electrical components are replaced, which is essentially impossible due to the massive number of parts required and the years it'd take for some foreign country to build them. We are all on life support in the form of the electrical grid. Both Obama and Trump recommended that measures be taken to harden the grid against EMP (and also Coronal Mass Ejections from the Sun, another source of the same end result), but the individual electrical power companies don't want to go to the trouble and expense, and the government hasn't mandated it.
Full report:
http://www.empcommission.org/docs/A2473-EMP_Commission-7MB.pdf
Executive summary:
http://www.empcommission.org/docs/empc_exec_rpt.pdf
Back to the 200 bad guys comment, the Federal Energy Regulatory Commission (FERC) says that there are 30 critical Substations in the US electrical grid, and that if any 9 of them are taken out of commission, the grid could go down for weeks, up to 18 months or more. When the snipers took out the Silicon Valley substation a few years ago, it was believed by some to be a test to see how easily a Substation could be brought down by rifle fire. It was child's play, according to authorities. Just some guys in the surrounding hills with rifles firing on the station for a few minutes.
The biggest existential threat to the inhabitants of the US is our own government's corruption and incompetence. Mostly the corruption, IMO, because it doesn't take a genius to figure out what needs to be done in a lot of these situations.