The strengths of Truss bridges are that Truss bridges can support and resist lateral loads. Another is that unlike the Arch and Beam bridges, the Truss bridge prevents twisting and swaying during earthquakes and high winds. Truss bridges also resist the forces of compression and tension.
Yes there were truss bridges in Europe before the United States. Truss bridges formed in the US because of Europeans, but new American designs were made and that is why the truss bridge is more abundant in the US than Europe today.