In my opinion (colored no doubt by my own status as an immigrant Muslim):
1. There is no way to stop all "radicalization", but the pool of available recruits would definitely shrink if public discourse WITHIN Muslim settings (media, community groups, politics, mosques) includes a healthy dose of counter-jihadi propaganda and a narrative which allows "reporters" to see themselves as doing a good deed, not as traitors to the cause of Islam.
Unfortunately, most of these recruits never run into anyone who vigorously challenges their views and has the vocabulary to do so. Most of the time, fellow Muslims will prefer to become quiet and slide away (or if they are exposed to left wing academia, nod in approval at this person's willingness to challenge the imperial war machine, while silently tut-tutting to themselves about some of the theological fantasies the brave rebel is spinning).
In this case, some family members seem to have argued more and even went so far as to inform the CIA..which I think is a reflection of Dad's status and awareness that his position in modern Nigeria could be jeopardized by this nut. In other cases, you may get warnings from friends or acquiantances. All that is more likely to happen if this option is in people's minds: that they can report someone going nutty and that such a report is actually a good deed and not "snitching" or treachery. For that to happen, examples of such reporting need to be amplified and broadcast as a good deed. Positive propganda...
The US govt can do only a little in this matter, but I am sure there are possible programs involving universities and media scholarships and whatnot that can have an impact. If they are not "official", that helps. But that presupposes that there are American planners who have an idea of what the narrative and counter-narrative should look like and on current form, I dont think the US govt is likely to perform too well in this area.
2. Once someone is "radicalized" (which really means that he takes orthodox Islamic teaching seriously AND then connects his Islamic obligations to the need to act against the great satan) he or she has to find someone willing to help out with the tactical part. He has to get the explosive or make it. If he or she remains isolated, it is virtually certain that he will fall into the hands of some intelligence agency (all the paintball jihadis and the clueless bastards who flew to Pakistan recently are in this category) but if he makes contact with actual trained jihadis, then he can proceed with the next step. What this means is that the crucial link in this process is the actual jihadi trainers and experts. There are probably none to be found within the US. Given the high level of radicalization in Britain, maybe you can find some there, but probably not even there anymore.
To meet them, you have to go to AF-Pak, Yemen or Somalia. There are probably some scattered through subsaharan Africa and Indonesia and Phillipines but the wannabe jihadis best bet is to fly to Pakistan or Yemen. Ergo, that is where you have to focus your intelligence energies. I dont believe this bull#### about grievances (very real ones like Palestine or partly manufactured ones like Kashmir) being the "root cause". Root causes are a dime a dozen. Its the trained people who connect "root cause" to actual bomb in rectum. There are a few thousand trained people and most of them are in Pakistan. When and if they are wrapped up, the threat is pretty much gone.
Can they be wrapped up? I dont know.
3. Airport security is important, but its the very last step. And the current system seems designed to create theatre more than focus on actually stopping someone. Intelligence should be able to identify most cases long before they get to the airport. But I will leave the details of airport harassment to the experts...