Canada: The Country on the Eastern Border of the USA

The question contains a geographic misconception: Canada borders the United States to the north, not the east.

Actual Borders

• North: Canada (5,525 mi / 8,891 km) — longest international border.
• South: Mexico (1,954 mi / 3,145 km).
• East: Atlantic Ocean.
• West: Pacific Ocean.

Canada–US Border Details

• Spans from Atlantic (Maine/New Brunswick) to Pacific (Washington/BC).
• 49th parallel (west of Lake of the Woods) + natural boundaries (Great Lakes, St. Lawrence, St. Croix River).
• 13 US states border Canada: ME, NH, VT, NY, PA (water), OH (water), MI, MN, ND, MT, ID, WA, AK.

Maritime Eastern Border

The US eastern boundary is the Atlantic Ocean. Maritime boundaries exist with:

• Bahamas (south of Florida).
• Cuba (south of Florida Keys).
• Bermuda (UK) (offshore).

Why "Eastern Border" Might Mean Canada

• In the Northeast (Maine, New Hampshire, Vermont, New York), the border with Canada runs roughly north-south but is often perceived as "eastern" because it's the easternmost land border.
• Historical: "Eastern frontier" in colonial times referred to the Maine/Canadian border.

So: Land border to the east? No—Atlantic Ocean. Land border to the north? Yes—Canada.