308.2 Creativity
"A work of authorship must possess 'some minimal degree of creativity' to sustain a copyright claim. [...] '[T]he requisite level of creativity is extremely low.' Even a 'slight amount' of creative expression will suffice. 'The vast majority of works make the grade quite easily, as they possess some creative spark, 'no matter how crude, humble or obvious it might be.'"
310.7 The Time, Effort, or Expense Required to Create the Work
"When examining a work for original authorship, the U.S. Copyright Office [...] will not consider the amount of time, effort, or expense required to create the work. These issues have no bearing on whether a work possesses the minimum creative spark required by the Copyright Act and the Constitution."
Note that this is not true in every country's copyright system (some do recognise effort), but it is true in the US.