I have asked this question before, but never really got a satisfiable answer: why do governments (not just USA/canada) spend these resources to check data physically at a border? It's not like you need to 'smuggle' any form of data physically. I mean, any data considered to be dangerous (like terrorist attack plans, atomic bomb designs or political inside information) can be accessed across borders via the internet.…
Most government can't do that (in theory...) when you are a citizen or maybe even just a resident, except when you cross the border. So if they want to watch you politically, they do that (at least) at the border.