More likely it might make it worse. In US political scene, people are divided strongly and therefore moderates gets to chose in the end. This is better and keeps extremist grabbing the power (well, most of the time). With range voting, power of moderates would diminish and it would be matter of which side has slightly higher number of extremists.

I think what would improve US elections is rather this:

Publish results in real time. Most people don't seem to realize consequence of not voting . If results comes in real time then people who are lazy might get extra prode. If 95% of the population votes, there is less likelyhood of nasty surprises as opposed to say only 60%.