If I noticed such on my bike I would experiment/investitgate a bit. One thing that comes to mind is if you are judging this while the bke is on the center stand, then it is possible your bike is not sitting "plumb" on its center stand. On a recent post quite a few folks noticed their bike leans to the side when on the center stand. That would throw off your perspective.
If that does not reveal the apparent problem, use half inch masking tape to mark a "T" on garage floor. Get the "T" to be very accurately square at the intersecton, use a framing square or such. Make the "T" wide enough to more than span the width of the grips on your bke and long enough to more than span the wheelbase. Park your bike and place in center stand with tires precisely sentered over the long line of the "T". You should be able to scoot the bike enough to center it up so that the center marks of the front and rear tire are each aligned upon the center of the tape. Drop a plumb bob from the end of each grip and mark the floor where the point of the bob touches. Use your frame square to mark the top line of the "T" at point perpendicular to teh plum bob marks. Use a tape measure to find the distances between those marks on the "T" top and the plumb bob marks. They should be equal if the handle bars are square. This will be a crude method and you may not get it to measur perfect even if it is perfect, but it should be very close.
If they are off quite a bit, either the handle bars or thier installation faulty or the frame swing arm joint is damaged (unlikely IMHO). The bolt holes in the handle bars may be large enough to let them be mounted a bit ****-eyed. I thin I have even heard of folks drilling out the rear most holes a bit to make them slot like so as to change teh spread of the bars.