WASHINGTON — President Joe Biden acknowledged Wednesday that the pandemic has left Americans exhausted and demoralized but insisted at a news conference marking his first year in office that he has “outperformed” expectations in dealing with it. He said he would likely have to settle for “big chunks” of his signature economic package to break an impasse in Congress and further attack inflation and the pandemic. Biden said he believes important parts of his agenda will be passed before the 2022 midterm elections and voters will back Democrats if they are fully informed — an assignment he said he will pursue by traveling the country. The president began the news conference by reeling off early progress in fighting the virus and quick passage of an ambitious bipartisan roads-and-bridges infrastructure deal.