Jan 4 (Reuters) - General Motors Co (GM.N) reported a second straight drop in quarterly U.S. auto sales on Tuesday, as semiconductor shortages and supply chain snarls hit production amid high pent-up demand in the country. The U.S. automaker said fourth-quarter sales fell 43% to 440,745 vehicles, compared with 771,323 vehicles a year earlier. General Motors said 2021 sales were at 2,218,228 vehicles, below Toyota Motor Corp"s (7203.T) annual sales of 2,332,262 vehicles.