1952. The Cold War. Seven years after the Bomb was dropped on Hiroshima. Two years before Gojira and its fantastical, but much more powerful, depiction of nuclear terror. The US is invaded by a nameless, clearly "Soviet" country, which drops A-Bombs everywhere, parachutes in lots of troops disguised in American uniforms and aims to "take over the free world".
Invasion USA is pure Cold-War paranoid propaganda. It makes no attempt to explore a realistic scenario for invasion of the USA, its politics being vague and jingoistic, but is content to "scare" with its imagery of a vast army of ruthless, Democracy-destroying enemies, huge flotillas of planes and "thousands" of nuclear bombs. Most interesting to me is the apparent lack of awareness of how, exactly, nuclear weapons work. The Enemy lobs them at airfields, aircraft carriers, dams, factories and cities with carefree abandon, apparently unconcerned that the territory they want to thus occupy will become an unoccupiable radioactive wasteland. Only once is radioactivity even mentioned. But where are the burn victims? Where is the discussion of how to deal with the lasting effects? Eventually, even New York is nuked; people are killed, sure (not nearly as many as in Hiroshima) but the buildings largely survive because of their exemplary "steel frames". Yeah, right. Meanwhile the US retaliates by hitting the Enemy's homeland with "three times" the number of nukes as had been aimed at the US. There are so many A-Bombs tossed around that very little should be left of the US, Russia or indeed the world. The fact that nuclear war can be depicted so casually in terms of conventional warfare (an A-Bomb is just like an ordinary bomb, only bigger) is the most fascinating aspect of the film, coming as it does so soon after the devastation of Hiroshima and Nagasaki -- but without real awareness of it.
Apparently Invasion USA had some impact at the time. (Hedda Hopper is quoted as saying, "It will scare the pants off you!") Its message is that America needs to fund the military, big-time, in order to be prepared for the inevitable invasion. Complacency will prove deadly. The scale, swiftness and nuclear thoroughness of the invasion is intended to drive the message home. And why not? 1950s Americans should have worried that not only didn't they have enough weapons (even though the powers that be unleash "three times" the number of nukes as the Enemy), but they also have, according to the film, an ineffectual and almost totally unprotected Government that can provide no guidance to the military whatsoever (what was the President doing, I wonder, apart from delivering bleak TV messages filmed from slightly behind his chair so that all viewers can see of him is his left ear?); a military that is unable to come up with a defense strategy of any kind; no advance warning system, nor a working intelligence community that might have detected the fact that the Enemy had been making thousands of A-Bombs or noticed that a vast army was being deployed long before it reached the US mainland; no civil defence strategies; and, apparently, no international alliances. Eek! This is the Super Power that will Save Democracy and the World? We're in big trouble.
Invasion USA revolves around a group of people in a bar in New York. They discuss government policy and the like, whingeing about taxes and expressing outrage at the idea that they should be forced to support military needs at the expense of their own profits. One of their number is a man with a supercilious air; we later learn that he is a prescient hypnotist. Suddenly the US is invaded, with the destruction reported and shown on a large-screen TV on the barroom wall. The group, panicked, split up to return to their various home states and in the course of the movie die through bomb attack, the nuking of the Boulder Dam and subsequent flooding, planes being shot down, etc. A woman and a TV reporter find love -- and then death -- when New York is attacked (giving the tale some romance and personalised tragedy). Then they all wake up and discover that the hypnotist has given them a glimpse into the future; the attack hasn't happened, but will, soon enough. They leave the bar once more, having learned that their selfishness and lack of patriotic foresight can only lead to destruction of all they value, the Senator to take up arms in the Senate, the industrialist to turn his profitable tractor-making factory to the construction of tanks, and one-and-all to generally exhibit more American patriotism and military zeal.
The movie is a primitive affair, though not without some propagandist effectiveness, I suppose. The acting, such that there is, is OK, but the SFX are pitiful. Most of the film is made up of stock footage of combat from WW2. Admittedly this footage is sometimes rather spectacular, particularly during the Pacific attack on US naval vessels. Nuclear attacks on mainland sites (such as the Boulder Dam and New York itself) are achieved by superimposing a nuclear cloud over the scene. Most effort is put into the attack on New York, which has some bits of rather nice model destruction and some decent collapsing walls. Likewise, there is an effective scene in which one of the bar-guys, travelling by taxi, makes it to his farm in time to learn that the Boulder Dam has been nuked and a wall of water is heading toward them. He bundles his family into the car and they run for it, unsuccessfully in the end. The sequence generates some decent suspense, despite the poor SFX.
Overall, however, there's not much to say about the film technically. It is only of interest as a socio-historical document, inuring the American populace into acceptance of the idea that the country must get itself into a state of perpetual war-readiness -- an attitude that has reached its apotheosis post-2000, with the country coming to accept not just perpetual war-readiness, but a perpetual state of war: there can only be peace if the country is continually at war.
Postscript: Chris Lawson, one of Australia's major SF writers, has expanded on (and expressed some disagreement with) aspects of this review. His excellent comments can be read here.