By virtue of being a citizen of a visa waiver country, you're considered a low risk to overstay. Since you don't need a visa, there is nothing technically wrong with leaving the airport and staying in the US - just because you wrote 'in transit to Canada' doesn't mean US Immigration didn't 'clock you in' to the US under the VWP.

If you were not from a visa waiver country, you would need a visitor visa to transit and would be admitted to the US under that visitor visa during your transit time.

The Transit Without Visa program was eliminated years ago.