What was the effect of Germany's decision to continue to practice unrestricted submarine welfare?

US embargo on trade--Germany used unrestricted submarine warfare in World War I as a means to cut off trade to and from Great Britain during the war.

Because so much of the US's trade was with Great Britain and they had claimed neutrality, the US was not happy to have their trade interrupted by Germany. The continued unrestricted submarine warfare led to the US stopping trade with Germany. This gave Germany more reason to be hostile toward the US and when they decided to continue despite embargoes and warnings, they sought the alliance of Mexico in what Germany thought would be eventual war with the US.