Buddhism Originated in India, where Gautama Buddha gained his Enlightement under a tree.
Their major principles was to always speak Truth, never harm any creature, try to help others.
In the US it is unlikely that Buddhism alone had any direct influence on laws, but because many of it's teachings about living a moral life i.e. not killing, stealing, etc. are the same as other more dominant religions it could be said that religious convictions (Buddhist ones included) in general have influenced lawmakers in making decisions.
Buddhism also affected other societies as many Hindu followers who were from lower casts joined it immidiately due to discrimination in their own religion.
Hope this helps!
