Indeed this has been discussed a number of years ago on FT.

This may be suggestive of what is captured and some sharing-related dynamics:

https://www.cbsa-asfc.gc.ca/btb-pdf/...cudes-eng.html

At the end of the day, I don’t see CBSA outsourcing risk assessment to CBP as realistic given part of the assessment is to determine eligibility to be admitted into the Canada. CBP officers are sworn to upheld US laws not Canadian ones. By extension, border control between the two countries could be removed as well.

I thought the contention was information sharing and access to another nation's law enforcement databases, not risk assessment. The latter is decision making while the former is just access to records and history. For example, CBSA, at its POE terminals, can query CBP records directly or via special access API for info on certain USA passport (travel history, DUI info, criminal warrants, and other derogatory information, etc.) Once the info is received, which should be fairly immediate, CBSA can risk-assess the traveler and either allow or deny entry. The same goes for CBP requesting info on Canadian travelers. The scope of info either agency can request or receive is agreed upon in advance, coded into bilateral legislation/agreements and, ultimately, built into the the software running in the terminals at either POE. Same with other countries as well and the Interpol, of course.

There's always a chance here for name collisions, inaccurate or false info stored in a database that could send a traveler to secondary inspection or worse. But that is the reality of aggregating data from multiple disparate sources into a single record.

I don't think it is just one obstacle (eg info sharing). It's also different eligibility for admission, political optics etc.

Take info sharing for instance. AFAIK (eg can't find any evidence of it) customs/immigration interaction is not shared. So if a traveler had a run in with CBSA with undeclared goods, that is not shared with CBP. It wouldn't show up in shared criminal databases. This would be exclude NEXUS membership from CBSA perspective.

Different eligibility for admission - As an example, Canada takes DUI more seriously than US in regards to determining admissibility. My understanding this difference in admissibility is the reverse for sex workers. Selling is not illegal in Canada (purchasing is) but both selling and purchasing is illegal in US.

You asking CBP officer who is sworn only to applying US laws/regulation to apply Canadian ones as well. IMHO it's a non-starter politically.

Definitely eligibility for admissions differs, and so do many other things, as you said. Look no further than arming CBP officers at enrollment centers as the simplest example. Sigh. I think in general we're violently agreeing here.