Wilmer McLean is reported to have said that "The war began in my front yard and ended in my front parlor" given that the First Battle of Bull Run occurred on his front lawn, and that later Lee surrendered to Grant in McLean's parlor. This is an indication of how locally concentrated the war really was.
When the Civil War was taking place, there were no planes, or transportation to bring in or out soldiers. Sometimes it would take them days to get to a battle, only to find they didn't get there in time. The sides did not have the Intel, technology, or transportation that we have today that helps troops.
Southern troops initially scored important victories scored victories, advanced as far north as Gettysburg, Pennsylvania and threatened to take Washington, D.C. at one point. Key battles were fought as far west as Texas and throughout Missouri, Kansas, Mississippi, Tennessee, Georgia and Virginia. Additionally, the first battle of ironclad ships between the Merrimack and the Monitor was fought at sea. In the minds of some people,, thew war continued to be fought throughout the country for many years after the truce was signed and still continues to this day.
No, the Civil War was not too locally concentrated. The Civil War involved fighting between all of the southern states and all of the northern states. Even if the fighting was concentrated in some areas of the south, this does not mean that the war was locally concentrated. It was a national war.