Do North American banks have a key phrase that allows customers to disable all security checks for using the card internationally?

No. Since the bank is the one that has to assume the risk of unauthorized charges (by law, your liability can't be more than $50), it doesn't matter that you are "okay with taking the risk," because it's the bank's risk. The anti-fraud measures are there to protect the bank and are not optional.

You might consider getting a card with a different bank, as their anti-fraud algorithms vary widely, and others may be less sensitive, particularly after you've been a customer for a while and they learn you travel frequently. Some banks also allow you to set a travel alert through online banking, which is much faster than calling. Other banks will handle fraud alerts through text messages or their app; you can just respond that a charge was authorized and have your card reactivated within a minute rather than having to make international phone calls and talk to customer service.

Canadian banks are indeed sensitive and most of the algorithms to check are automatic. That being said, not all foreign transactions are treated suspiciously but when they are, it is very inconvenient as this is something that caused me issues several times.

Calling your bank ahead of time is not an obligation but a recommendation but that reduces the cases when the suspicious activity alert is raised. I have had particularly frequent issues with Mastercard from Citibank Canada (at the time) and got them to dial it down to a more reasonable level for many years by insisting on the phone and getting escalated to a higher level agent. Some banks now allow you to enter your travel plans electronically which is more convenient yet still an annoyance.

With the conversion to credit cards with chips that happened over the last few years, alerts have been reduced somewhat but I did get into trouble for particularly odd timing. For example, spending at home in Montreal than starting to spend away in and booking a hotel for my next destination or buying a gift remotely for someone. This sequence of transaction location really get them, so what I do is switch cards to break down the hops across countries. I can do this since I have credit cards with 5 banks in Canada but that does not apply to everyone.

Some destinations are, according to the bank, more suspicious. For example, all online transactions I did with Brazil were blocked but I did manage to make some in person while there. I did complain and did not get much of an answer other than the system did not authorize.

The more you travel with regularity, the more the algorithm adapts to your patterns. Also some banks are more drastic then others. As I mentioned, Citibank tends to block transactions while Tangerine lets them through usually and calls to verify suspicious transactions which at least does not leave you stranded somewhere unable to purchase gaz or pay your car rental before taking your flight home. These things happened to me when I had fewer cards or in places where only one worked such as Iceland where gas stations are mostly unattended and only HSBC worked.

It's likely your bank is extra-sensitive to international purchase risk because you have only lived in Canada for a few weeks, so your Canadian account is very new. If you lived here several years and traveled regularly you probably wouldn't have the issue.

All I can suggest is to have a mobile phone number that's affordable for the bank to call, and have it on file. Many banks will let a charge through, even if questionable, then call you to verify it was legitimate. (My bank, BMO, does this.)

I can't answer directly w.r.t. law or bank policy, but a way to mitigate the issue would be to use either 1. an internet-based bank (safer than it sounds, Ally or Bank of Internet for example) and/or 2. A card that has specific features for international travel (Charles Schwab high-yield investor checking Visa, for example). I traveled internationally for a year with one of each of these and there were times I was in three different countries in a week - I never had any issues with fraud prevention (except one time where they successfully detected fraud) and never paid an ATM fee or an excessively high currency conversion. I also never informed anyone of my plans.