Counting subsea boundaries (continental shelf) Canada borders:
Canada in the north and Mexico in the south have land borders with the US.
Mexico and Canada
Canada and Mexico
Canada and Mexico.
Mexico and Canada.
Mexico and Canada
Canada and Mexico
Canada only has a land border with the USA but has maritime borders with Greenland and France.
Canada and Mexico.
Canada and Mexico
Pennsylvania borders Canada by water across the 51 mile frontage on Lake Erie, but Canada and Pennsylvania do not touch land borders.
That would be Canada.