Does that not work pretty much the same everywhere? On the rare occasion that I drive across the SR520 bridge across Lake Washington, they have no problem recognizing my Oregon plate and sending me a bill. Same when I drove through the Bay Area. Took them a couple weeks.

It does work pretty much everywhere, the catch is that some places will only bill you the toll amount. Other places will bill the toll plus a small convenience fee. Others will bill the toll and a huge penalty on top. Are you confident which jurisdiction you are traveling though? Has it changed since the last time you visited?

In northeast US, you get mailed a $50+ fine on top of the toll for not having an EZ Pass transponder.

That's harsh. Do they have tollbooths for visitors, then? Seems like the places I've been on the west coast with toll roads have ditched the actual toll booths and just use license plate recognition for billing cars without a pass. No penalty, but you get a discount if you have a pass.

Yes, there are toll booths. You pay with the time you spend waiting in line though.

The catch is that Canadian e-tolls are run by a private, foreign company which has been handed over PII for Americans by their own government.

That's a very broad statement.

TReO, the tolling system for the Port Mann bridge in BC before it was detolled, was built by a Vancouver-based company: https://oxd.com/work/treo-tolling-website/

And run by the TIC: https://www.ticorp.ca/

That is a political problem though, which seem easier to rectify than a technical problem.