Given the timing of Oumuam's appearance, during nuclear tensions with Russia, N. Korea et al, and given that the speed (10% of light speed) and diameter of the "asteroid" are in the bounds of the size and performance of an Orion. So, it appears as though the asteroid Oumuam could be a Orion Space Battle Cruiser. This is how America controls the strategic high ground of space.
Sources:
http://www.slate.com/articles/health_and_science/science/2017/12/scientists_are_watching_oumuamua_an_asteroid_they_think_could_be_an_alien.html
EDIT 03 November 2018
https://arxiv.org/pdf/1810.11490.pdf
