In act 1 of Macbeth, the Scottish forces are at war with Norway. Macbeth and Banquo are both military leaders who contribute to the victory over Norway. Macbeth is even awarded with a new title—Thane of Cawdor—in recognition of his service. The former Thane of Cawdor, MacDonwald, has betrayed King Duncan of Scotland by fighting with Norway. Therefore, in the first Act of the play, Scotland faces enemies in Norway and in the treacherous MacDonwald. 

Later in the play, once Macbeth is King of Scotland after murdering Duncan, the rightful heir and Duncan's eldest son Malcolm has fled to England in fear for his life. He is supported by the King of England and later Macduff, another high-ranking Scottish thane, joins him there. They recognize that Macbeth is a terrible, corrupt, and tyrannical king, so they plot to attack Scotland. They want to oust Macbeth from the throne and place Malcolm as king. In this case, Scotland is being attacked by England, but because Macbeth is a tyrant, the readers hope that England wins the battle. In fact, they do, and Macduff beheads Macbeth, vowing to let his severed head stand as a reminder of what happens to tyrants in Scotland. The play closes in the hopes that Malcolm's reign will restore peace and justice to Scotland. 

In Macbeth, the kingdom of Scotland faces two enemies. First of all, it faces the combined force of Macdonwald, the thane of Cawdor, and the army of Norway. Together, these forces hope to defeat King Duncan and remove him from the throne. However, as we see in act 1, scene 2, they are no match for "brave" Macbeth and Banquo, who demonstrate great skill in battle. Macbeth, for example, kills Macdonwald by cutting him from the "nave" to the "chops."

Secondly, the kingdom also faces an enemy in the form of Macbeth himself. After killing Duncan and taking the throne for himself, Macbeth becomes a violent and tyrannical king. He is so focused on protecting his crown that he kills Banquo and Macduff's family, for example. Therefore, in act 5, a force led by Malcolm (the true heir of Scotland) storms Macbeth's castle. In act 5, scene 8, Macbeth is beheaded by Macdff and his death restores peace and order to Scotland.

At the beginning of the play, the enemies are Norway and traitors and rebels within Scotland itself.  In Act 1, sc. 2, we hear of how Macbeth was victorious in battle against Norway, against the rebel Macdonwald, and against the traitor, the Thane of Cawdor.  The Thane of Cawdor had aligned himself with Norway in trying to defeat Duncan's forces.  By Act 5, Macbeth's enemies are most of the people of Scotland.  Malcolm, having fled to England when his father was killed, has gathered English forces to back him in his efforts to unseat Macbeth.  Macduff has joined with Malcolm in the attempt.  In Act 4, sc. 3, Macduff tells Malcolm how bad things are in Scotland under Macbeth's rule. Most of Macbeth's Thanes have left him and he is nearly on his own by the end of the play.

At the start of the play, the kingdom of Scotland faces two enemies: Norway and a rebellion led by the Scottish traitor to the throne, Macdonwald. Both enemies are essentially overcome on the battlefield. First, Macbeth and Banquo fight the rebels, led by Macdonwald. The injured captain tells Duncan that

brave Macbeth (for well he deserves that name)

Disdaining Fortune, with his brandished steel [...]

carved out his passage

Till he faced the slave [and]

unseamed him from the nave to th' chops" (Act I, Scene 2, lines 18-24).

He paints a vivid mental picture of Macbeth, slashing through a thicket of bodies to forge a path to Macdonwald, and, once he reached the leader, Macbeth thrust his sword through the man's stomach and ripped him open all the way up to his jaw.

Then, the captain explains, just as Macbeth and Banquo were turning away from their victory over the rebels, the Norwegian king saw his opportunity to attack while they were tired. The king then brought a fresh army, and even though Macbeth and Banquo were clearly alarmed by the prospect of another battle, "they doubly redoubled strokes upon the foe" and won (Act I, Scene 2, line 42). Scotland, then, really owes its safety to the bravery of its champions on the battlefield.

Another way to answer the question posed is to look at the two specific character from Macbeth which are enemies to Scotland.

Both Macbeth and Lady Macbeth can be identified as enemies to Scotland. First, both are adamant about claiming the crown for Macbeth. At first, Lady Macbeth is the first of the two to declare war on Scotland by deriving a plan to kill Duncan (the king of Scotland). Macbeth, at this point, is perfectly fine given he has just been named the Thane of Cawdor. Instead of murdering Duncan immediately, Macbeth wishes to keep his title a little longer and not proceed with Lady Macbeth's plan.

We will proceed no further in this business:
He hath honour'd me of late; and I have bought
Golden opinions from all sorts of people,
Which would be worn now in their newest gloss,
Not cast aside so soon (I,vii, 31-35).

It is not until later that Macbeth realizes that he is at risk of losing the throne and he begins to make plans of his own. When Lady Macbeth questions him regarding his plans, he tells her

Be innocent of the knowledge, dearest chuck (III,ii,45).

Macbeth has finally taken control over the issues which have begun to arisen and has made plans of his own.

Therefore, both Lady Macbeth and Macbeth are the two enemies to the kingdom of Scotland (as seen in the play, Macbeth).

As for other enemies (or countries) of the kingdom of Scotland, the third link below is another answer about how Norway and the rebels within the Scottish borders are also enemies of the kingdom.