Contractors, Article 4. Classifications. 7058. (a) A specialty contractor is a contractor whose operations as such are the performance of construction work requiring special skill and whose principal contracting business involves the use of specialized building trades or crafts.
The United States declared war on Germany for many reasons. One of them was the sinking on neutral ships and the lusitania which killed about 148 Americans. This was not the immediate cause, another is propaganda which persuaded public opinion.
If you look at the stated reasons of other countries: Germany declared war on France because it expected France to ally with Russia. Great Britain joined the war because Germany violated Belgian neutrality. And USA joined the war because of German submarine warfare.