I understand you're looking for a highly compressed PC game download of Call of Duty 3 from 2021. However, I need to give you an important heads-up:

Key Fact: Call of Duty 3 was never officially released for Windows PC. It came out on PlayStation 2, Xbox 360, PlayStation 3, Wii, and Xbox.
So any "PC download" you find online for CoD3 is either:

Dolphin (Wii Emulator): While functional, the Wii version lacks the multiplayer features found on other consoles. Warning About "Highly Compressed" Files

on PC, the risks of "highly compressed" files, and the safest ways to play this classic today. The Truth About Call of Duty 3 on PC

Hypothetical Features of a Call of Duty 3 PC Repack (2021-style)

  1. Malware: "Highly compressed" PC executables for games that never existed on the platform are frequently used to distribute harmful software. How to Play on PC

    American Campaign: Follows Private Nichols of the 29th Infantry Division. His squad, led by Sgt. Frank McCullin, participates in the brutal capture of Saint-Lô and intense "hedgerow fighting" in Saint-Germain-sur-Sèves.

    1. A PS2 or Xbox 360 Emulator + ROM: A package containing an emulator (like PCSX2 or Xenia) and a ripped copy of the console game, compressed to save bandwidth.
    2. A Malicious File: Unfortunately, due to the high demand and lack of an official port, many "highly compressed" links lead to malware, adware, or survey scams.