Oregon has a mandatory insurance law (ORS 806.010) which requires that every driver insure their vehicle. The basic minimum liability insurance a motorist must have is:

• Bodily Injury and Property Damage Liability of 25,000 per person / $50,000 per accident for injury to others and $10,000 per crash for damage to the property of others.
• Personal Injury Protection (PIP) of $15,000 per person.
• Uninsured Motorist Coverage of $25,000 per person / $50,000 per occurrence for bodily injury.

Bodily injury is a lot like compulsory third party (CTP) in Australia. It covers you when your vehicle hurts or injures someone in a motor vehicle accident. Property damage liability is like Australian third party property car insurance. It covers you for damages you may cause to someone else's property; usually a car but it could be a fence, post, etc.

Oregon's personal injury protection (PIP) coverage pays for medical, rehabilitation, funeral, and child-care expenses as well as for loss of earnings and in-home assistance if you and your passengers are injured in an accident, regardless of who is at fault.

In Oregon, the coverage is called Property Damage Liability to cover the damage to the other party's property or 3rd party in an accident. 

PIP is Oregon’s version of no-fault insurance. It al­lows you and your passengers, regardless of who caused an accident, to have insurance coverage for “reasonable and necessary” medical, dental, hospital, surgical, ambulance, and prosthetic ser­vices incurred within one year after the date of an injury up to a maximum of $15,000.

Uninsured Motorist (for bodily injury) normally covers a policyholder, the insured members of your household and passengers for bodily/personal injuries, damages or death caused by an at-fault uninsured or hit-and-run driver. If your son was involved in an accident where the other driver is at fault but has no insurance, your son's policy should cover his medical expenses, up to the limit on the policy.

The average auto insurance policy in Oregon cost around $825 but the actual cost for your son's insurance may vary since there are rating factors such as where he lives, his driving record, etc. He will need an OR driver's license since most insurance companies will not carry his insurance with only an Australian license. To get a quote for you son in Portland, OR follow this link for a car insurance policy.