To add to Ken's comment, you can add a USD bank account (in addition to your CAD account) in your dashboard settings and your USD transactions will settle into USD without any conversion fees. If you click on 'Add bank account' in the payouts tab [0], there's an option to add a USD account. CAD transactions will automatically settle in the CAD account associated with Stripe. USD transactions will automatically settle in your USD account associated with Stripe.

[0]https://dashboard.stripe.com/settings/payouts

Source: I work at Stripe