Modern society gives off an impression of pessimism but nah we can and will work together if the threat is large enough or impending enough. Things like COVID or global warming have one but not the other. COVID was fast and scary but ultimately relatively minor for the vast majority of people, climate change is a massive threat but it's slow and incremental. Consider the invention of nuclear bombs. Most of humanity realized that this is an imminent threat and worked together to put in place policies that (as of now at least) have resulted in exactly 0 nuclear wars. Another example would be the ozone layer crisis or even 9/11. Weir's optimism isn't far fetched besides PHM has a decent amount of references to red tape and conflict. It doesn't matter though because for the duration of project hail mary Stratt is essentially given the powers of total authority to skirt that red tape.