This is a well acted, scripted and directed film. The SFX are good as is the cinematography. I cannot see where the criticism has come from, especially with the unique twist at the end. Yes it may seem a bit odd that all the cast are British and therefore why set in the US etc, but I cannot imagine people are that pedantic or petty.
Agreed this isn't Alien, The Thing etc but it does not deserve the level of negativity.