During World War I, the United States declaration of war on Germany (1917) came after Nicholas II had abdicated as a result of the February Revolution. When the Tsar was still in power, some Americans resisted fighting a war with him as an ally.
The U.S. entry into World War I (1917) happened after Nicholas II had stepped down as a result of the February Revolution. When the Tsar maintained his authority, some Americans opposed fighting alongside him as a co-belligerent.