Why did the u. s. avoid involvement in wwii until december 1941? why was the pearl harbor attack such a shock to the u. s.?

The U.S. wanted to remain neutral due to public dissatisfaction with how the great-war(ww1) had turned out. War with Europe was the last thing on the American people's mind until we were attacked by Japan: we did not expect the attack from Japan, so this act alone shocked and angered the American public and government that, in turn, declared war on Japan by vote.