I don't think it is possible in the near future for an invasion of America to take place. The boardering countries have fractions of a percentage of the millitary power America wields. Any seaborne invasion from any fictional "EU Empire" scenario or "Superpower China" scenario would be seen way off due to the size of the logistics for such an invasion and promptly sunk. Bikinni attol would have nothing on what happens to that fictional fleet.
The only way to get at America is through blockade of things like oil.