This passage in Isa 19:23-25 cannot be removed from its context which begins back in V16 and earlier (V1). The prophecy in this chapter can be split into two parts:
- V1-15 is a prophecy about Egypt and how God will punish Egypt in various was and effectively destroy their economy in order for the people to turn back and acknowledge the LORD.
- V16-24 is a prophecy about Egypt AFTER it has returned to the LORD.
in the second part of the prophecy, a number of specific predictions are made about what Egypt and Egyptians will do "in that day":
- V16 - Egyptians will tremble at the uplifted hand of the LORD of hosts
- V17 - the land of Judah will bring terror to the Egyptians
- V18 - Egypt will speak the language of Canaan (Hebrew) and swear allegiance to the LORD
- V19 - an altar to the LORD will be erected in Egypt
- V21 - the Egyptians will worship and acknowledge the LORD
- V23 - highway between Egypt and Assyria, ie, going through Israel and Judah
... and so forth. It is abundantly clear that these prophecies have never been fulfilled up to the present time. The key is the significant phrase (V16, 19), "in that day" which often refers to either the first or second advent of Jesus or His ultimate kingdom of peace (space precludes a full discussion of this point.)
Therefore, I suggest that the prophecy in Isa 19:16-25 is about Egypt AFTER the LORD returns to establish is kingdom of peace.