I remember the Garfield episodes and quickies, but not any U.S. Acres. I distinctly remember wondering as a kid "why do these guys appear in the intro even though they're not in the show at all?". I was wondering if they were there Just Because, kind of like how the dog and the cat sometimes appeared in promotional pics for the comic even though they didn't play much of a role in it.
...oh wait, now I get it. I was looking into this, and according to some websites, in my country they cut out all the U.S.Acres segments from the cartoon. That would explain it.