Answer:
The Involvement of the United States in WW2 was the attack on pearl harbour by the Japanese who where in a alliance with Germany so the domino effect took place once The USA declared war on Japan Germay retaliated by declaring war on The US
Step-by-step explanation:
Decmber 7 1941 suprise attack from the Japanese
caused a domino's affect as japan was member of the pact of steel an alliance between Germany and Japan