Might have been asked before and probably a silly question.
I normally fly AC but travelling to the US on United this time.

Given "Customers traveling to and from Canada in United First are eligible for United Business access."
Flying United Frist class from Canada to a US destination via a US airport should grant me access to the UC at my transit point.


I'm flying YOW-ORD-BOS tomorrow, my boarding pass have no indication about my lounge access (AC boarding pass has clear indication about lounge access granted or not), they even try to upsell me when I book the ticket.
Do I scan my YOW-ORD boarding pass to get in or ORD-BOS?