[Skybird]

The technical reliability was in doubt until the end anyway.

It saves money of a nation that mounts and mounts its debts, and already needs the good will of even rivalling nations in order to maintain it's economic survival.

It increases chances for improving geostrategic relations with Russia, whose good will is as important for America as is China's.

In case of Iran continuing it's missle program, Obama left open the option to pick up the missile defense again. That is not so important, since the threat to europe is from nuclear proliferation and terror bombs anyway. From an american perspective it may be seen as an encouragement to Europe to take better care of it's defensive interests itself

But it would need to pay for it with money european nations in depts and deficitary budgets again do not have. In fact the British are considering to abandon their nuclear submarines and aircraftcarriers. Well, we have gone bancrupt over too wasteful ways of living, so what do you expect? Endless business as usual...?