When you marry a US Citizen and have stayed over 6 months in Canada. The RCMP National Repository holdings is often required by the USCIS
(Department of Homeland Security U.S. Citizenship and Immigration Services). This is called the Privacy Act.

https://travel.state.gov/content/travel/en/us-visas/Visa-Reciprocity-and-Civil-Documents-by-Country/Canada.html

The Privacy Act is based on a fingerprint search and will contain a copy of the data in National Repository of Criminal Records as it exists.
A copy of your fingerprints is not included in the report.
The report may contain criminal record information that would not normally be disclosed during a criminal record check, such as a record suspension (e.g. pardons or sealed youth records).

Please confirm whether you require the Privacy Act form or not.
The Privacy Act is mailed directly by the RCMP to your mailing address with Canada Post which has no tracking number.
This is why we ask you for a US or Canadian mailing address so there is less risk.