The Lost Missile (1957)
A fusion-powered alien rocket is hit by a Soviet missile, causing it to circle the Earth at 4,000mph, at an altitude of 5 miles, vaporizing everything it flies over. It's on a path toward New York, and will eventually torch most of the earth. Victims include a dogsled, a French-Canadian family, and the city of Ottawa.
This movie has most of the tropes on your B-movie bingo card, and one thing that makes it a must for Rifftrax. It's got a mysterious alien threat. It's got young scientists in love at a government lab with an atomic pile and a super-duper new nuclear missile. It's got stock footage of military planes and radar stations, with a narrator talking over the stock footage. It's got the same cheesy effects shots used over and over. It's got trigger-happy Russians, gossiping housewives, guys in Civil Defense helmets and hoodlums in leather jackets. But above all else, it stars ROBERT LOGGIA.