Really don’t understand the point you were trying to make. The reason why it spread so fast early on is because we had so many unforeseen super spreader events early on. Like the guy in New York that came back from China, went to a party and infected a whole bunch of people. The town of New Rochelle was a hotspot early on. Throwing a net over that city would have prevented the spread early on.
There is a reason many island nations that lock down their borders early on have had a much lower impact and slower spreading.