Bludgeoning, piercing, or slashing damage are the most common types of damage in the game. Nearly all monsters have at least one attack with one of those damage types. Barbarian’s are so resilient because their rage makes them resist this.
If you just replace a race’s “Resistance to Acid” by “Resistance to Bludgeoning”, it’s a decent power-up. It might not be OP, that would require a race-by-race analysis, but from my perspective, if I had to choose between resistance to one of the elemental types and one of the physical, I would ALWAYS choose one of the physical to resist to (unless I was a Barbarian). And having a choice that seems to always best another isn’t good design.
If you lessened one of the race’s other benefits, it would probably be balanced, but again, this requires a case-by-case analysis. If you intend to explore this further, I’d pose a homebrew analysis question on its own.