In the U.S educational system, would a GPA below 3.25 really disadvantage a student?
Given that the US system for undergraduates implies a broad education with a bit of specialization (the major), it is possible to achieve such a GPA in a large number of ways. Students "majoring" in, say, mathematics in the US have less than half of their coursework in maths. The rest will invariably include literature, history, the social and physical sciences, etc. 

If you want to do graduate study in mathematics, coming from such a curriculum, it might matter a lot where you got B's and lower. If you do well in "major" courses it is easier to make the case for math than if your lower grades are concentrated in your major. 

But, in general, 3.25 isn't horrible, but it isn't great. But graduate schools look at more than a number (any number) when choosing students. They look for indications of success as expressed in the coursework, but also in letters of recommendation and statements by the candidate. Some students, however, are "grade driven" and will do nearly anything to achieve a high GPA, even if they have to sacrifice learning to get there.