So rather than the US minding its own business and getting the differing levels of law to agree, they just make impositions on other sovereign nations?

I'm not OP but it's probably just short of impossible it could chance upon a fossil of any sort of multicellular organism. Based on Earth history, we have evidence of microbial life from approximately 3.7 billion years ago.

The first evidence of multicellular organisms don't appear until circa 600 million years ago, so evolution took 3 billion years to advance from single to multicellular life.

From our observations of Mars, it is believed the last water would have dried up around 3.7 billion years ago. Its approximate age is 4.6 billion years, or around the same age as Earth.

Taking what we know about our own planet it is fair to say that any single celled organisms on Mars didn't have long enough to evolve to become multicellular, assuming there ever were any single celled lifeforms there in the first place.