This amusing film centers around a small European nation that devises a rather unusual method for dealing with serious economic difficulties. The Grand Duchy decides to invade the United States! With only spears, shields, and lances, they arrive in New York harbor without encountering any resistance. The reason? Their Prime Minister, "Rupert of Mountjoy" (played by Peter Sellars), had anticipated being arrested, which would provide him an opportunity to plead the case of his Sovereign, "Gloriana" (also Sellars), against a Californian vineyard threatening to flood the market with inexpensive wine—the only product “Grand Fenwick” exports. However, upon arrival, they discover the city is empty because everyone is participating in a required nuclear preparedness exercise. The resourceful "Tully" (naturally portrayed by Sellars) formulates a plan to exploit their situation by abducting the renowned scientist "Kokintz" (David Kossoff), who’s working on a powerful “Q-bomb,” and returning home. Suddenly, this tiny country becomes the focus of worldwide attention; everyone is worried about this dangerous device, and "Tully" finds himself captivated by the professor's daughter, "Helen" (Jean Seberg). Two outcomes appear equally likely: either “Grand Fenwick” will become the richest nation on Earth, or—well, there won’t be a world at all. Sellars performs admirably, but Kossoff steals the show with his portrayal of the quirky scientist, and Austin Willis also provides some genuinely funny moments as the completely bewildered US Secretary of Defense. It doesn't elicit constant laughter, but its ridiculous premise offers an entertaining critique of weapons of mass destruction and larger nations dominating smaller ones; it’s generally a pleasant experience.

Source on TMDB