This precious stone set in the silver sea,
Which serves it in the office of a wall,
Or as a moat defensive to a house,
Against the envy of less happier lands,
This blessed plot, this earth, this realm, this England.
As you can see, Gaunt makes much of England's being an island. The only trouble is, it isn't one! Both in Gaunt's time and in Shakespeare's, England had a land border - not only with Wales, which the English had long since anschlussed, but with Scotland, a sovereign state.
Of course, the Scots today are used to English people and others conflating England and Britain (the Americans seem very prone to it), but I'm puzzled that the habit dates, not only from before the 1711 Act of Union, but even before the crowns were united under James VI and I. This inability to see Scotland is clearly a condition of long standing, which I propose to give a medical name: "ascotia". Was Shakespeare's Gaunt the earliest sufferer, or is it still older?