Characters names are references to 50s sci-fi stars. John Agar, Kevin McCarthy, Jeff Morrow, Richard Carlson, Roy Gordon, and Julia Adams.
If this is supposed to take place in the 1950s the American flag should have 48 stars, or 49 if it takes place on or after July 4, 1959. The flag is a 50 star version which wasn't in use until July 4, 1960.
When the mini "land jellyfish" emerge from behind the large one, for the first few seconds they don't have their jellyfish heads.
The English subtitles consistently misspell "all right" as "alright".
At 39:05 the soldier holds the woman with his left hand over her mouth to prevent her from screaming. With his right hand he holds a knife threateningly against, not her throat, but against the back of his own left hand.