Americans save little but borrow a lot. The Treasury is now delivering pandemic stimulus payments through direct deposits and mailed checks. Credit: U.S. Secret Service HONG KONG – There is nothing like a pandemic to expose systemic differences. For China and the United States, which were locked in an ideologically driven competition even before the Covid-19 crisis, those differences are stark. But the two countries have at least one thing in common: when this is all over, they will need to rethink their social contracts. To curb virus transmission, China and the U.S. have implemented social-distancing measures, which — together with the unemployment they produce — have broken the cycle of earning and spending that sustains global growth. The International Monetary Fund estimates that world GDP will contract by 3 percent this year. China’s shrank by 6.8 percent in the first quarter. Yet the type of public-health measures pursued — and their outcomes — have diverg