"Given the involvement of individuals considered deities in some cultures (Thor, Loki), there is even the potential to classify the event as an 'Act of God', although that designation would be subject to strenuous theological and legal debate."
The new Avengers movie may have been insufficiently realistic for the U.S. military to be willing to lend its resources but it's also apparently not so fantastic that it can't be subjected to real world damage assessment.
The Hollywood Reporter enlisted a company called Kinetic Analysis Corporation to figure out the actual money cost of the damage done in the course of the Avengers defending Earth. (I noticed their seismic computer model is called MIDGARD, so I'm guessing someone there already had an eye for Thor.)
The report itself (pdf) is mostly hilarious with serious treatment given not only to The Avengers movie, but citing other monster movies as if they're real-life precedent.
While gratitude over repelling the invasion will persist in the short term, in the longer term the events leading up to the opening of the portal will in all likelihood be examined in detail, and that immunity probed for legal weakness (recall the regulatory and legal consequences to the Ghostbusters over the Gozer incident of 1984).
At the same time, Kinetic Analysis Corporation's real world business is literally deadly serious. Included in the report are references to lessons learned on 9/11, for example about the damage a collapsing building can do to underground infrastructure. As whimsical as the exercise is, to see the damage evaluations listed alongside the real cost of Japanese tsunamis and earthquakes and Hurricane Katrina is sobering.
By the way, their final number on the economic impact?
KAC expects the physical damage from the invasion to be $60 to $70 Billion Dollars, with secondary economic impacts from cleanup, loss of business, disruptions to commerce and services, etc. causing an additional $90 Billion dollars. Casualties are undoubtedly in the high thousands. Therefore, we estimate the total economic impact to be at least $160 Billion dollars
"In addition, there was considerable collateral damage of questionable necessity by at least one of the S.H.I.E.L.D. operatives (Hulk)."