Answer:
Because the Act introduced the first ever quotas of a numerical nature limiting the number of immigrants that would be allowed in, It should that nativisit and isolationist sentiment was strong in the US.
Step-by-step explanation:
America, in the 1920s, had become more nativist and isolationist. After the first world war, Americans was striving the maintain the image of America as a nation of immigrants from western and northern Europe and this Act sought to primarily prohibit the influx of Easter and Southern Europeans. They deemed these groups as undesirable.