Does "have a bearing on" also mean "impact"? No.
Can someone help me to understand this phrase? I shall try.
Having a bearing on an object is an effect of sharing a trait with a demonstrable effect; impact on the other hand, is a cause to an effect upon another object.
Let's take @FumbleFingers' example:
This explains why archeologists are so careful to record the depth at which objects are found - the depth usually has a bearing on the age of the find.
The depth of the earth in a given location is an effect of the conditions at the time it was deposited. An archeological artifact deposited at a given depth in a given location is an effect of the conditions at the time it was deposited. Thus the depth of the earth is having a bearing on the age of the find because the age of the earth at that depth and the age of the find should be the same.
So, to sum up:
- Impact causes an effect on an object
- Having a bearing on is a demonstrable effect of a trait shared between objects.