> 90 years of independence? <
The point is that Lithuania gained its status as an independent nation in 1918. And although they were occupied by the Soviets from 1939 until 1990, they were still recognized by the U.S. and many other countries as an independent nation for the entire time.
The same was true for Lativia and Estonia. For all three nations, their Legations (Embassies) in Washington DC never closed, and their diplomats were always accorded fully accredited diplomatic status by the USA.
Lithuania's Independance Act, declared on February 16, 1918 came as a result of World War One, which saw Russia yield to Germany after the Bolshevik Revolution.
Lithuania's neighbours Latvia and Estonia, as well as Ukraine and Belarus also regained their statehood at around the same time.
The maps I have seen of interwar Europe look like this, without an independent Ukraine or Belarus (even called Byelorussia or White Russia): http://users.erols.com/mwhite28/euro1935.htm