if i buy a regualr ipad just wifi in rhe united states will it work in canada

AppleCare+ is only valid in the country of purchase. As such, if you intend to purchase the optional AppleCare+ plan, you will need to purchase this cover in Canada.

Generally, you should aim to purchase a device in the country within which you intend to spend most time - as this significantly simplifies the warranty position should you ever need to call upon it.

Here is Apple’s Warranty statement as applied to devices purchased within the US:

Legal - iOS Warranty Document Us - Apple

As for an iPad purchased in the US, it will be fully functional in Canada and other countries.

Yes, it will work in Canada fine.

Apple Care+ as well as the one year warranty is normally only available in the country of purchase. However, for Wi-Fi devices Apple stores may honor it and repair or replace it at their discretion.