This is the largest ever shipment of methylamphetamine bound for Australia and the largest ever domestic seizure of meth on record in the US.
USA authorities have seized 1.7 tonnes of methylamphetamine, worth approximately $1.29 billion, destined for Australia.
Another 25kg of cocaine, worth about $9.5 million, and 5kg of heroin valued at $2.6 million, was also uncovered in the shipment of 850 auto audio parts.
Police said the drugs could have led to more than 17 million drug deals.
Police in Victoria, as well as the Australian Federal Police, worked closely with a security taskforce from the US's Homeland Security department to seize a consignment of drugs allegedly hidden in two containers claiming to contain audio equipment. Six people have been arrested for their alleged involvement.
"If this shipment had made Australian streets it equates to something like 17 million hits of ice".
The Australian Federal Police have warned Australians one of the largest Mexican drug cartels is targeting the nation..
Assistant Commissioner Hill is urging ice users to get help.
"They have been sending smaller amounts over the years".
Three raids in Sydney on Thursday led to the arrest of two men aged 25 and 31, and seizure of 2kg of cocaine.
"The Australian public who are consuming ice and other illicit drugs are assisting organised crime to flourish", Mr Hill added.
Three of those arrested, including the American couple, were due to appear in a Melbourne court Friday on a charge of attempting to import controlled drugs.
"They are one of the major and most powerful organised crime cartels now operating", Mr Hill said.
James Carouso, the US acting ambassador to Australia, said in a statement that "this historic seizure highlights just how important the US-Australian partnership is in protecting Americans and Australians alike".
Dr John Coyne, head of the Border Security Program at the Strategic Police Institute, told Neil Mitchell "it's further evidence (international drug cartels) are expanding into our space for distribution".
The operation also involved raids in British Columbia on Thursday by the Royal Canadian Mounted Police, which resulted in the seizure of "a significant quantity" of suspected proceeds of crime, police said.
The people arrested allegedly have connections with a California-based organised crime syndicate.
The previous record of seized methylamphetamine bound for Australia was 1.3 tonnes found in Western Australia in December 2017.