This is science NOT opinion.
The most basic way to test this thesis is by direct comparison. As of 6 April, seven US states had not adopted shelter-in place orders and their stats are in line with those that did even when adjusting for population density.
Open the country!
Those seven states that did not adopt stay at home policies are more rural and more isolated. Had they adopted the same policies as California and Washington State early on, its likely several of these states would have suffered no deaths at all to coronavirus.
You want a real example about how travel bans and proper testing, contact tracing and isolation policies work, look at
TAIWAN!
TAIWAN is a country of 24 million people more exposed to China than any other country in the world. John Hopkins University predicted TAIWAN would have a higher infection rate and death rate than any country in the world. Instead this is what happened thanks to TAIWAN's anti-pandemic policies:
TAIWAN total infections: 429
TAIWAN total deaths: 6
Now compare that to the United States:
UNITED STATES total infections: 849,092
UNITED STATES total deaths: 47,681
Taiwan proves that early travel bans, testing, contact tracing, and isolation when needed works. TAIWAN successfully protected its population, while the United States remains in an ongoing national crises it has never seen before with human health and economic side effects on a massive scale. TRUMP failed and the scale of Trump's failure is reflected In the difference between the number of deaths in TAIWAN from coronavirus vs. the number of deaths in the United States from coronavirus.
But TAIWAAAAANNN!
Yes, they reacted early, because of their traditional distrust to China. But they're also disciplined people, who care about their country, and not to mention homogeneous country with no racial problems.
Can you compare New York City and Tokyo?
As of today, city of New York has 12287 deaths.
Tokyo, the world's largest and densest city, has 93 deaths.
New York is locked down.
Tokyo was never locked down.
Both cities got the virus about the same time, yet New York city death rate is over 250 times higher than Tokyo's.
Apparently, virus is not biggest problem. The filth is.