canada
It is up to you to balance between the risk of your application being deemed insufficient and the effort to honestly reconstruct all your itineraries in the past five years to neighbouring countries (which you may honestly not be able to accurately recall, or can be mistaken), depending on your personal circumstances and risk tolerance.
Depending on the circumstances, you can attach an explanation (the full history does not fit anyway on the form) letter, listing all countries you regularly visit, justifying the circumstances (e.g., you live in a border region, you are a cross-border commuter, etc.), and providing as much reasonably useful information as you can (e.g., the frequency of your visit, statement that you cannot accurately recall, rough estimates of the date and duration of your visit).
This does not guarantee that the IRCC will be satisfied with this level of information (though in the past there were cases where it is accepted with this level of detail for e.g. cross-border commuters; it is not helpful for the visa officer to know the exact details of every trip to France a Monaco or Geneva resident makes) or that your application would not be refused. However, if you provide reasonably detailed explanation for your travel history, even though it is not to a single-trip precision, you would unlikely be "directly or indirectly misrepresenting or withholding material facts relating to a relevant matter that induces or could induce an error" in the processing of your visa application.
You should however accurately list your trips where reasonably detailed data is available (e.g., electronic record from the U.S. via I-94 records) and of course any trip you made to Canada, as well as any trips with significant durations.