There were very few willing to join the banner of the black, red, and gold or white rose, and fee who did join lived to tell there tale.
Sophie Scholl's last words were "How can we expect righteousness to prevail when there is hardly anyone willing to give himself up individually to a righteous cause. Such a fine, sunny day, and I have to go, but what does my death matter, if through us thousands of people are awakened and stirred to action?"
As you say, there were few who had the courage and many of those gave their lives for the struggle. In America, we have some more hope because we have a gun culture. Many people in the US are just armchair cowboys who probably wouldn't rise up and do anything. But we certainly have a good number of folks who have the will, and the means, to stand up and say "No".
The average German should have feared Nazi medicine. Before the Jews were killed, the government sent euthanasia personnel around to get rid of the old, infirm crippled and mentally ill to reduce the financial load on the government. The government decided who fit in those categories and when.