“Thousands of tonnes of rock getting impacted by a few hundred pounds is unlikely to produce any significant change.”
But what if it carried a nuclear bomb that went off on impact?
https://scitechupdates.com/comet-impacts-formed-continents-when-solar-system-entered-arms-of-milky-way/?fbclid=IwAR0lWww-bj7LkGNuf9WiahDDCbiAUWB4_c1W1giApq24c7LH8XgVphJ-JbE