If your CRA account shows that you have RRSP credits, you can make an RRSP contribution. Too late for 2022, but the contribution carries over to 2023 and beyond. Don't know about RESPs, but expect the rules to be the same. You cannot shield the RRSP contribution from US taxes - it cannot be treated as US pre-tax and excluded from your US income if you live in the US. If you lived in Canada and have US-source income, you might be able to exclude the income as exempt foreign-source income (Form 2555 and Sched SE Adjustments [manual entry in Part II, line 9 - TTax doesn't ask you]), but only if you meet the rules of having no residence or office in the US.
Do you file Canadian taxes? If so, the RRSP contribution is a pre-tax exclusion. If you don't file Canadian taxes, I'd wait until you return to Canada and make the RRSP contribution then. But, you make up your own mind - it may be worth it to you to make it anyway.
