Why did the government restrict immigration in the 1920s?

I think it was because there were too many immigrants coming in and taking our jobs, and American decided figure out what was an actual American, (so like the first settlers), and the immigrants weren't  
"American" I actually think they limited china on how many people could come into the US and then after so many people came they cut them off, and then the Chinese who wanted to come to America would have to wait until next year. But then they considered that un American I guess unconstitonal is the word and then undid that law. I hope this helps.