COVID-19 deaths and cases in the U.S. have climbed back to levels not seen since last winter, erasing months of progress and potentially bolstering President Joe Biden’s argument for his sweeping new vaccination requirements. The cases — driven by the delta variant combined with resistance among some Americans to getting the vaccine — are concentrated mostly in the South. While one-time hot spots like FL and LA are improving, infection rates are soaring in KY, GA and TN, fueled by children now back in school, loose mask restrictions and low vaccination levels.