The two strikes in the northern village of Mustabaa on March 15 "caused indiscriminate or foreseeably disproportionate loss of civilian life, in violation of the laws of war," HRW said in a statement.
At least 25 children were among those killed, it said, reiterating its call for an end to arms sales to Saudi Arabia, which is leading an Arab coalition battling rebels in support of Yemen's government.
HRW said that it conducted an on-site investigation and found remnants of "a GBU-31 satellite-guided bomb, which consists of a US-supplied MK-84 2,000-pound bomb mated with a JDAM satellite guidance kit, also US-supplied."
The accusation came as US Secretary of State John Kerry visited the Gulf for talks with Washington's traditional allies, including Saudi Arabia, which has led a military campaign against the Huthi rebels since March 2015.
"One of the deadliest strikes against civilians in Yemen's year-long war involved US-supplied weapons, illustrating tragically why countries should stop selling arms to Saudi Arabia," said HRW researcher Priyanka Motaparthy.
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"The US and other coalition allies should send a clear message to Saudi Arabia that they want no part in unlawful killings of civilians," she added.
HRW said the strikes on the market may have also killed 10 Huthi rebels.
The UN children's agency UNICEF said at the time that the air strikes killed 119 people, including 22 children.
Rights groups have repeatedly urged the United States and other nations to stop selling arms to Saudi Arabia, accusing it of causing heavy civilian casualties in Yemen.
Around 6,300 people have been killed in the conflict since March 2015, more than half of them civilians, most of whom died in coalition air strikes, according to the United Nations.
The Iran-backed Huthis seized the capital Sanaa in September 2014, forcing the internationally recognised government to flee.