I donated to US charities & sent a tax receipt for the US value of my CAD donation.Can I claim these donations without having any US income-I can convert it back to CAD?

You can only claim donations to US charities as a deduction against US income. The exceptions would be:

• if you live near the border in Canada throughout the year and commute to your principal workplace/business in the US, and if that employment/business was your main source of income for the year.
• if your gift is to a U.S. college or university at which you or a family member is or was enrolled in
• if your gift is to a registered U.S. university in the list of qualified donees which you can find here: https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/p113/p113-gifts-income-tax.html#P99_6372