US vaccinates since december. Now, 15 million people in the U.S. have received both shots," Nearly 25 million additional people in the country have received their first vaccine shot." The USA have 328.2 million inhabitants. For herd immunity you need ~70%...
Do you really think, if reaching a herd immunity, suddenly nobody will infected or die?
...and please remember, the USA are not an island... you must think international...