It would be suicide to attack the US
If Russia, Venezuela, N. Korea, and Iran were to team up and attack the US, it would be suicide. Maybe at the least we will have five minutes warning that the missiles are incoming, plenty of time for the President and a qualified representative from the military to key in the codes for the nuclear football. The only thing that could possibly undermine that is if they were to attack the US while Biden has his nap. That would be very sneaky of them.
You can bring down the entire US electric grid by destroying ten major electrical substations. I doubt that is the plan because if you were to do that it could take months even years to get them all repaired. However, if you have a small tactical nuke similar to what hit Hiroshima or Nagasaki and you hit 30 or 40 major cities you will wipe out the entire US electrical grid (provided you are strategic in your targets, Texas is separate from the grid and the Mississippi sort of divides the grid in half). They began rebuilding Hiroshima about 4 years after the blast so done correctly these places are not left uninhabitable. There are 40 naval bases in the US, you can be sure they would be targets, but the poseidon torpedo used to attack the coasts would cause tremendous devastation to the ports. Oil refineries would be another major target. However, if you take out the electric grid you will also take out pumps that pump oil and gas, and so shut down the entire trucking throughout the country. You will cause mechanics to also cease without electricity. You don't have to worry about the army because they will be overwhelmed trying to keep order in the US if there is no electricity and no trucking. All the cities will starve. You will have looting and chaos. But the description of a millstone being tossed into the ocean as a picture of the destruction of the Great Babylon is very plausible. Within a single hour this could happen just as the Bible says, all the merchants of the world would weep knowing that the US as a customer is over, and the stock markets would sink like that millstone and just as fast. Within that hour the US dollar would be worthless. When 3 buildings near wall street were destroyed on 9/11 it came very close to collapsing the US economy and insurance industry. What we are talking about here is a ten block radius in 40 cities as well as all naval bases and most of the US coastline.