No it is not baseless fear mongering, a small unmanned sea vehicle can easily transit an entire ocean given enough time especially if it sits low in the water like a “narco sub” type design, we aren’t talking about hard limits on missile ranges here.

Further see designs such as the Sail Drone or Australian Blue Bottle that can easily wander across much of the world on low to almost no power use while employing sensors and potentially even weapons (as in the case of the Sail Drone).

Japan was able to lob weather balloons over the US during WW2, floating a simple long endurance drone launch vehicle across the Pacific Gyre into range of a western US city is absolutely feasible.

Now… if it was the Ukranians we were fighting, they would have already figured out how to do it on mass and would be hitting US littoral infrastructure everywhere, but thankfully we aren’t facing such a competent maritime military, yet even still the possibility is absolutely within the realm of reason and for political objectives it may very well be worth the risk and cost for an actor like Iran to do.

As I have pointed out elsewhere in this thread, it is not something to fear as some kind of apocalyptic mass destruction and shahed attacks, the distance as you have pointed out is far too great for that.

However, a handful targetted to create maximum media panic and influence US politics? That is an entirely different calculation, your attack will work even if the execution is utterly bungled so long as somebody discovers the wreck of your unmanned vessel wrecked on the shore of the West Coast and reports it to the police.

As a final note, your self assured smugness that the US could not come under attack is well inline with historical US naivety around the imperviousness of the US from attack because “that stuff is happening over there far away”. It is well documented how the US failed to properly convoy commercial shipping along the East Coast of the US during WW2 for an egregious length of time even as German U-boats were sinking ships left and right off the US coast. The British in particular got really pissed off that they would convoy a shipping fleet across the Atlantic and then the US would take over in US waters and then leave the door wide open to a U-boat sinking the ship 50 miles from its destination US port after it made it all the way across the Atlantic.

The fact that the U.S. Navy was so unprepared to deal with the arrival of U-boats on the U.S. East Coast has been roundly criticized by many historians, especially since the U.S. Navy had been engaged in an undeclared war with U-boats for many months before Pearl Harbor. Much of the blame has been heaped on King, some deserved, most not. The unlikeable King makes for an easy target, but there were many factors that resulted in what was effectively a disaster as great as Pearl Harbor in terms of ships sunk and lives lost. British naval Intelligence provided timely warning to the U.S. that the first U-boats were on the way, but little was done with it. The Commander of the U.S. Eastern Sea Frontier, Rear Admiral Adolphus Andrews, had very little to work with, at least initially, with only 100 or so aircraft along the entire coast, and a number of U.S. Coast Guard cutters that were brought under Navy command. Given the lessons learned from World War I, the U.S. failure to immediately implement a convoy system along the U.S. East Coast has attracted a lot of historical “analysis.” There were certainly cases in which U.S. destroyers were inappropriately apportioned, and some were occasionally idle in port while merchant ships were being sunk almost within sight. Nevertheless, the destroyer force was actually heavily tasked and generally in very short supply. Most were committed to escorting transatlantic convoys providing troops and critical war materials to the British war effort, and others to escorting U.S. Navy ships operating in the Atlantic to guard against forays by the German surface navy, as the battleship Bismarck had done earlier in 1941.

What the U.S. sorely lacked was the large number of small anti-submarine craft (“sub-chasers”) like the hundreds that had been hastily built in World War I, but no longer existed. With insufficient escorts, King, Ingersoll, and Andrews reasoned that congregating coastal merchant ships into inadequately protected convoys would only make the U-boats’ job of sinking large numbers of ships even easier and more efficient. This was not because King was anti-British or anti-convoy, but a matter of scarce resource allocation. It was, however, arguably arrogant on King’s part to initially refuse the British offer to send smaller escort ships to the U.S. east coast. By this point in the war, the British had those types of small escorts in comparative abundance, which is how they had ended the U-boats’ first “Happy Time” in 1940. Eventually, the U.S. relented, and in March 1942, the British deployed 24 anti-submarine trawlers and 10 corvettes to the U.S. East Coast to assist, and 53 Squadron of the Royal Air Force Coastal Command (flying U.S.-made Lockheed Hudson aircraft) operated out of Quonset Point, Rhode Island

https://www.history.navy.mil/about-us/leadership/director/directors-corner/h-grams/h-gram-008/h-008-5.html

Never EVER listen to journalists when they tell you war is new, only listen to people who actually have studied war because the lazy narratives people repeat are ahistorical, very misleading and totally turn you around from understanding things as they truly are and how they fit into the context of military history.