Because govtech is notoriously difficult to break in to.
Peter Thiel abusing government backchannels.
> What's preventing a Canadian competitor from doing the same?
A lack of access to corrupt government backchannels.
Government procurement takes a lot of time to see through to completion; Palantir is not a new company, they're over 20 years old now. To succeed you also need money for lobbyists; regardless of what you feel of them they are a necessary part of the system. Also at the government level, especially at the level of federal governments, you are competing with Oracle, IBM, and other similarly large companies which is difficult to do if you are a new, small company.