Dear helpful people!

I have a question about duty/customs which I hope someone has the answer to!

I am travelling to Canada next week, but for reasons of availability for ff-miles redemption, the only way I could do it is via Seattle. I will be in the country for about 24 hours (in fact, almost to the minute).

I am bringing items for friends in Canada, consisting both alcohol and gifts above the duty-free levels.

Obviously I will complete forms and declare, but do you know if I would likely to be assessed for taxes in the US (fully expecting to be in Canada)?

Many thanks in advance