I don't know where you got that 5% number, every number that comes up in a search is above 2/3 to 70% to 90%. For example, just one link:
"Moreover, public opinion polls taken over the last five years have consistently found that roughly 70 percent of Americans think the United States should not make it easier for illegal aliens to become citizens (Figure 4)."
Different question altogether.
That could mean that people don't want the government to make it easy for illegal aliens to become citzens.
There's a whole lot of space left open by that statement, and nothing in it conflicts with the posted numbers.