"c. They said there was no more room in the country to take in more immigrants" was not usually an argument given since the nation was still expanding to some extent, with plenty of room in the midwest and west.
Your question is one which we still face today in our country. Immigration laws for our country were first written in 1790. Through the years additions and subtractions of the laws have taken place. But even today 2 of the most prevailing fears which Americans have are: 1) losing their jobs to those who are willing to work for below minimum wage, 2) what was once a prevailing white society many people are still afraid that people from other ethnic groups will become the #1 group in America.
