As a reminder, there is a difference between Israel and Judah. At this point in the chronological reading, the nations were separated, never to be joined again, until Jesus returns. The nation of Judah (plus the tribe of Benjamin) is known as the Jews. The rest of the tribes “the lost tribes” have been dispersed, many of them into the western nations.

Isa 19:19
In that day there will be an altar to the LORD in the heart of Egypt, and a monument to the LORD at its border.
The land of Egypt in ancient times was divided into two parts; upper and lower Egypt. The boundary between these two nations is in the area of where Cairo and the Great Pyramid are today. Interestingly, the pyramid is located both on the border of and in the heart of Egypt.

In the Millennium:
Isa 19:23
In that day there will be a highway from Egypt to Assyria. The Assyrians will go to Egypt and the Egyptians to Assyria. The Egyptians and Assyrians will worship together.

God sure uses an unusual sign (Isaiah’s nakedness) to demonstrate the humiliation of Egypt and Cush at the hands of the Assyrians.

Isaiah foretells that Judah will reject the truth.
Isa 30:9-11
These are rebellious people, deceitful children, children unwilling to listen to the LORD's instruction. They say to the seers, "See no more visions!" and to the prophets, "Give us no more visions of what is right! Tell us pleasant things, prophesy illusions. Leave this way, get off this path, and stop confronting us with the Holy One of Israel!"

In other words, they were saying, “Tell us things we want to hear”. Isaiah warned about this and so did Paul.

2 Tim 4:3-4
For the time will come when men will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear. They will turn their ears away from the truth and turn aside to myths.

Turning “aside to myths” is comparable to worshiping God on pagan high places. Do we do that today? What did God warn about that?

As always God gives us a chance for redemption.
Isa 30:21
Whether you turn to the right or to the left, your ears will hear a voice behind you, saying, "This is the way; walk in it."

Can’t you just imagine Him whispering this in our ears? This creator of the universe, caring enough about us to whisper in our ears! Amazing!