Radical Islam not only affects Muslims but it affects non-Muslims too and I'm not just talking about attacks. Such an extreme version of Islam breeds distrust among neighbors and fractures the delicate bonds holding societies together. All sections of society, in particular, Muslims need to become proactive and tackle this threat head on.
The growth of radicals in general has been a problem in America since its beginning. The first thing we need to do, is remember, that one group of radicals does not mean it is an epidemic of catastrophic proportions, we must understand the point of view and reasons behind the actions. America, as much as I love this country, likes to panic about everything, Agent K, from Men in Black, said it best; "a person is smart. People are dumb, panicky dangerous animals and you know it." The actions of the group was devastating, but I wouldn't call it a problem that cannot be remedied.
There are very few "radical" muslims in America. The muslims who are here are mostly peaceful, God loving and God fearing people. THey have a range of political and socail beleifs and not all of them are extreme conservatives like the media choses to portray them. Some simply follow a differnt cultural calendar.
While largely not publicized radical Islam has been present in the United States since the fall of the Shah of Iran. Many fled the former Persia to come to America. Not all were true refugees; some came at the opportunity to spread their beliefs and to practice in secret for years.