Best car for freeway driving?

I'm a Senior citizen preparing to move to a large city where I will have to do a lot of driving on Freeways. Coming from a small country town this really scares me -- and I'm afraid it'll scare me to death. It's time for me to get a newer model car and I want to trade in for a small car that has the oomph to get me safely on the freeway. Would a Honda Civic be a good choice? Should I look for one with a lot of horse power or would I just be wasting gas money? (I'm not an agressive driver so I need a car that will respond well when I finally grit my teeth and decide to merge into the rushing traffic)