The terrorists choose England as the springboard into

the US because the Great Britain is the closest ally of the US. The terrorists would think that the Americans pay the least attention toward people from England so they have more chances to sneak into the US.

They will probably have few more attempts (to get in) before they consider to stop if all fail.

I think that FBI does protect the American lives but not sure how effective it is.

Not necessary "white terror". The americans had been taught a lesson of too much freedom during 911. I think that the government should focus more on domestic issues and protection. Securing border and stopping influx of "free illegal immigration" is the priority.