After you load funds to your BitPay Card, the value will remain in US dollars. Supported cryptocurrency is converted to US dollars when it is sent to BitPay for loading the card, so it cannot be returned to your cryptocurrency wallet.
The cryptocurrency balance within your BitPay Wallet (and its estimate in USD) is not loaded to the card until you load it via paying a BitPay invoice. Only funds loaded to the card are locked in as USD. How do I add funds to my BitPay Card?