- US Passport > Irrelevant, get off your high horse
- It's a government rule, pretty standard in most countries, many in fact require 6 months of validity
- It is always solely the traveler's responsibility to ensure they have the appropriate travel documents, often people book tickets prior to obtaining travel documents (passport and/or visas), in fact for some countries the ticket is required in order to obtain a visa

You need to chill out.