Two creation stories. Two flood stories. And now two stories about the origin of the nations. Get the hint? The compilers of Genesis love this sort of stuff.
Here we are again with one language. That means we can take this as yet another account of national origins. After all, we've already read about the origin of different languages in 10:5, 20, and 31.
Traveling from the east, people settle in a valley named Shinar.
They decide, "let us make bricks" (11:3 NRSV), and then, "let us build ourselves a city, and a tower with its top in the heavens, and let us make a name for ourselves; otherwise we shall be scattered abroad upon the face of the whole earth" (11:4 NRSV).
This sounds like a good plan. People like at least their names to live on after they die. And besides, the tower can be a way for them to stay together.
Now the deity (here his nickname YHWH or Lord is used again) pays a visit to the tower.
In another very human-like portrayal, God "goes down" and "sees" (11:5). Recall that this deity also walks in the garden, grieves, and enjoys the smell of Noah's good cookin' on the sacrificial barbie (3:8; 6:6; 8:21). This is typical of the story-teller who uses the deity's nickname Lord (Hebrew: YHWH).
The deity reasons that with one language, these people can do anything. They've already built a tower to the heavens, which is God's territory.
So the deity proposes, "let us go down, and confuse their language there" (11:7). That'll confuse the pants off these little ambitious mortals.
It's kind of similar to God's logic for banishing Adam and Eve (3:22-24) and for limiting the lifespan of mortals (6:3). These people need limits or they'll usurp the very deity that created them.
Who is God talking to and who's the "us" of 11:7? Here we have more evidence of several otherworldly beings with the deity (also, 1:26-2; 3:22; 6:1-4).
The Lord scatters the people, which is exactly what they feared in 11:4. The Hebrew story-tellers love this kind of symmetry. If you pay attention, there are many other examples as the story unfolds.