Re: Not being an American
"Have I understood this right? In the USA citizens who wish to do their legal and moral duty and pay money to their government have to use a third party commercial company to do so."
No, it's not that bad. Even in the US, you can download the forms, print them out, and mail them with a check or money order. You may still be able to get blank forms at libraries. The forms are PDFs. Some at least are "fillable PDFs" and maybe by now those actually work in some PDF readers. Personally, I downloaded the forms, converted them to jpgs, used an emacs org mode table to compute the taxes, and filled them out using image magick to overprint the values onto the forms.