[Pontiac]

“The Civil Rights Act of 1964 was proposed by President John F. Kennedy in 1963 and later signed into law by his successor, President Lyndon B. Johnson, in 1964.”

Proposed by Kennedy, yes.

But would it have passed without Kennedy's death?

Kennedy's assassination generated a great deal of sympathy towards his goals.

[ansel12]

It would have passed, and so would the immigration laws that JFK ran on and which were his long time dream.