The Lusitania was a British ship. It is not included in the seven U.S. merchant ships the German U-boats sank.
Out ‘old colonial lords’ were then a democracy, and our closest allies, and they have continued to be our closest allies. Germany was a monarchy and an empire and they were not our allies and neither would they be until we had defeated them again in WWII.
We took the ‘side’ that our ships are free to trade with anyone at any time and cannot be sunk in international waters without it being an act of war.
Maybe you think Germany can dictate who we can trade with and where our ships can and cannot go on the open seas. I don't recognize their sovereignty in that sphere, and neither did the U.S. congress.
England is our ally. Germany is either at your feet or at your throat. Good thing we kept them at our feet! Dirty Huns. ;)