Germany sure enlargened would would've been a regional war. It was looking out to be just a fight between Austria-Hungary and Serbia/Russia. Then, Germany declared on France and Russia and invaded Belgium to bring Britain and eventually the US in the war.
I do not think it an understatement when they say that the first world war was a senseless, avoidable and unnecessary war. There was an air of national greatness and hubris that permeated all the powers, not just Germany. Concerns of empire, spheres of influence and entangling alliances caused the participants in 1914 to act in ways they would not have had all the above not been in place (parallel circumstances are in place today with this country but that is another matter for a different thread).
Regarding the part of your statement about Germany bringing the US into the war is I believe backwards. The US stated its official neutrality while it manufactured and shipped large amounts of munitions to England, France and Russia not to mention large bank loans to the Allied side. Germany warned us repeatedly about this and they were not attacking "neutral" shipping when they sank US ships. We did not have to get involved in that war and the ramifications of the fact that we did are still being played out to this day.