"Since your coast guard and your customs are those being responsible for the security in American ports this alarmism is difficult to understand from the outside."
Maybe you haven't read the articles about the weaknesses still present in our Coast Guard port security. Look up the thread titled:
"Port Security Is Still A House Of Cards"
I'm sorry Europe doesn't yet understand our "alarmism" as you say. We still remember well the lives lost and damage done on Sept. 11, 2001, so forgive us Americans for being still deeply concerned about national security.
Hopefully, Europe will not have to see greater damage before fully understanding our point of view.
Personally I do not believe that it is possible to control the boarders of such a huge country effective enough to shut all the bad guys out. If your Coast Guard or other authorities are ineffective you simply have to reorganize them. This incompetence has nothing to do with the ownership of a port. When I was a student in univercity I worked for some time in the harbour of Hamburg to finance myself. Although German police and customs are among the best in the world, it wouldn't have been a big problem to smuggle things or persons there. Once our police found 4 Russian antiaircraft tanks (tanks not guns!) from the former NVA (East German Commie Army) that were sold from the BND, our secret service, to the Israelis without any permission in some containers ;-). By fluke (or by a mischance - whatever you like) they were found by the customs.
Therefore - keeping people from the Middle East out of your country and its markets will cause severe damage but will not help you to provide security. In the best case they are only insulted, in the worst case it could happen that the dollar is replaced by the euro as the leading currency in the long term.