I am travelling in the United States on an A-2 visa (foreign government officials and employees). I want to see Niagara Falls, but heard that the view from the Canadian side is better. Can I go to Canada to see the falls and stay there for the night?
A temporary visa for the US does not imply any sort of right to enter Canada. Canada, being a separate country, has its own visa policies.
If citizens of your country would normally need a visa to enter Canada as a tourist, then you would also need a visa. A visit to Niagara Falls would not count as any kind of official government business.