Re: Really? Harmful contamination? Really?
Regarding your concern about overreach of sovereign claims, it looks like the legislators over here have already taken steps to keep that in check. Based on the text of the bill it seems that private individuals and corporations can only lay claim to resources that they can gather and bring back. So technically even if, say, Elon Musk sticks a US flag into an asteroid alongside a mining machine, the asteroid itself does not belong to us or him - the only things he can claim are the rocks dug up, and only if he can get them planetside. Furthermore, there's a clause that explicitly states that nothing in the bill is intended to lay claim of sovereign rights over any extraterritorial body.
Now keep in mind I'm American, so this could be bias on my part, but I think the idea behind the Space Act in an international context isn't necessarily to supercede international regulation of extraterrestrial resource exploration and exploitation, but rather to drive it forward. Keep in mind that the private sector is what is driving the space exploration industry at this time, and a good majority of the companies making plans to move beyond Earth are either of American origin or based in America. Amazon, SpaceX, Boeing, et cetera.
I agree there needs to be international regulation regarding the rights of both sovereign states and private individuals to explore outside of our planet, but the international treaties that currently exist are outdated and somewhat archaic. Ideally, what we're trying to do here is get the ball rolling. By passing the legislation America is trying to encourage people to actually do the thing and get out there, and prove to the world that you can make a profit from space rock. Once they do, other companies and nations will follow, and this will motivate everyone to update the existing international regulations to match the times and the technology. In the end I think extraterrestrial resource mining is something that is going to benefit everyone on the planet - it's a new frontier that will cause a rapid advance in our scientific, industrial, and technological prowess as a species. But someone has to take the first step.
Then again, I am American and therefore may have a colored viewpoint compared to the rest of the world - and also, the scenario I described above is assuming our government is acting with benevolent interests. Which I really hope they are, but given their track record...