A few points:
First, the definition of "contraband." The fact that small arms ammunition was carried on the Lusatania was not denied at the time. It was only denied that this constituted "contraband."
Second, the Germans in their official statement on why the Lusatania was sunk did not mention anything specific except that she was "armed with guns" (that was untrue) and "had large quantities of war material in her cargo" which could only refer to the small arms ammunition.
Third, nothing has been found in the wreck of the Lusatania which would add to that list of "contraband" small arms ammunition.
Finally, since the Germans very publicly warned the ship and its passengers before they sailed, I'm not sure how it matters what the Lusatania was actually carrying, or whether that met some strict definition of "contraband."
The bottom line is: Germans did not win friends or influence people in America by sinking ships with American passengers.
Shrapnel shells are not small-bore rounds, for example.
That the Wilson administration concealed their knowledge of the specifics of her war materiel cargo is unquestionable - the term of art then - contraband.
That that denial persisted for over a half-century is clear. Only actions external to the US government's position caused the truth to the revealed.
The parallels with Pearl Harbor, some 68 years on, are there as Hoehling, Farago, Stinnett, Wilford, Willey, Victor. ... , etc., and repeated denials of pointed FOIA requests show.
And, to add, Wilson "did not win friends" in Britain when he did not act to have a declaration war against Germany in 1915. More on that path perhaps when the remaining Admiralty files on the SS LUSITANIA are released?
And, finally, FDR recall did not pursue a declaration of war having several "incidents" in the Atlantic either. Did Stark talk too much?