How can I persuade my parents to let me come back to the U.S. during the summer when it’s not the best time to travel?

Or should I just ignore them and run away and book a flight back?

I don’t know anything about your relationship with your parents, so my response will have to be a very general one. Here is the Massachusetts page on policies for re-opening businesses: mass.gov/info-details/reopening-massachusetts. If they’re not comfortable with those precautions, that’s up to them. If you’re over 18 and have your own source of money, you can make whatever decision you want, but think long and hard about the long-term impact on your relationship with your parents.