Unless the amount that you received includes money that you contributed to the RRSP then all of the distribution is taxable.  

Your Canadian tax with held that was paid to the US would go under estimated payments.  Canadian tax with held that was paid to Canada is not deductible - only the actual taxes you paid to Canada are deductible as foreign taxes paid.

do I report the net amount? that is gross distribution minus the canadian tax withhold?

You will report the gross distribution to the US since you are filing US resident.  You would need to contact/file Canada to get a any refund of taxes mistakenly withheld there.  

I'm confused by your answers.

Here is another answer I found on this forum that is very different:

subject: 

Reporting Canadian RRSP Withdrawl on US Taxes

If you report your RRSP distribution as $10,000 you will be taxed by the US on that amount.

To get credit for $2500 tax paid to Canada, you would need to enter this amount as a Foreign Tax Credit, which is deducted from the US tax you owe on the Total Distribution amount of $10,000. 

If you enter your Taxable Amount as $7500, you will only be taxed by the US on $7500 and not need to claim the $2500 you paid to Canada as a Foreign Tax Credit.

However, most choose to report the Total Distribution and take the Foreign Tax Credit, since the 25% Canadian Tax amount is more than your US tax bracket would likely be. 

Hope this helps!

Total Distribution is the actual total amount of the RRSP distribution.
Taxable Part of Distribution is the taxable amount of the RRSP distribution using Pro-Rata rule depending on your cost base calculation:

• For Canadian citizens who are U.S. residents (but not U.S. Citizens), the amount of contribution including interest, dividends and any realized capital gains up to the day a person becomes a U.S. tax resident is considered principal (cost basis) for U.S. tax reporting purposes. The cost basis does not include any unrealized capital gain.
• For a U.S. citizen who is also a tax resident of Canada, your principal contribution to the RRSP will be your cost basis. Further, if the contributions were deducted on your U.S. Form 1040 income tax return, then your deduction does not increase cost basis.
• Cost Basis Defined: Cost Basis is what the U.S. considers the original cost of property or an asset, adjusted for depreciation.
• Reference: https://akifcpa.com/how-to-treat-resp-and-rrsp-canada-distributions-on-u-s-income-tax-returns/

How about a US Citizen who was once a Canadian tax resident but no longer files taxes in Canada but receiving the RRSP distribution with CRA withholding 25%?