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.
Mexico never considered going to war with the US, and America declared war because Germany was so desperate to buy time in Europe that they were willing to violate the borders of the United States. Economics had little to do with the reasons the US joined the allies.