Eurasian Milfoil is not indiginous to the US.  It was most likely introduced in the US in the 1940's

Eurasian Milfoil can be a very hard vegetation to control once established. Milfoil usually spreads best in slow moving water.  Eurasian Milfoil can quickly spread and crowd out other vegetation.  Milfoil can also hinder recreational activity as well as make fishing very difficult.  Milfoil can be tough to treat.  Submerged treatments such as using a Diquat & Cutrine mixture can spot treat this vegetation. Keep in mind diquat is a contact herbicide and will only kill what it touches.  Fluridone, at this point is still the best treatment for Eurasian Miloil.