Lt. Richard Burrows was the first American to cross into German territory in World War II. Unfortunately, he was also the first ground casualty in Germany.
https://archives.library.illinois.edu/erec/University%20Archives/2620076/33rd%20Armored%20Regiment%20After%20Action%20Reports%2C%20Log%20Book%2C%20and%20Eaton%27s%205%20Stars%20to%20Victory/10_5%20Stars%20to%20Victory%2C%20Robert%20Eaton.pdf