As unprecedented as it is to expect one to prove the negative, when dealing with the prejudiced and intellectually lazy one must go the extra mile:
http://www.vatican.va/holy_father/benedict_xvi/encyclicals/documents/hf_ben-xvi_enc_20090629_caritas-in-veritate_en.html
http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_const_19651207_gaudium-et-spes_en.html
http://www.vatican.va/holy_father/paul_vi/apost_letters/documents/hf_p-vi_apl_19710514_octogesima-adveniens_en.html
http://www.vatican.va/edocs/ENG0214/__P6.HTM
http://www.vatican.va/roman_curia/pontifical_councils/justpeace/documents/rc_pc_justpeace_doc_20060526_compendio-dott-soc_en.html#In friendly dialogue with all branches of knowledge
Fail!
I say first that too large a number of US Bishops really do not get how Catholic social teaching applies to a representative democracy such as ours is (or used to be?)
Second: the Church's teaching on government does not, cannot, support thoroughly any particular system or society, BECAUSE European socialism, aside from its support of awesome levels of immorality, works against both solidarity and subsidiarity.
Of course, Socialists will claim Vatican Support, but those claims will always gloss over the particular moral issues and the all important issue of subsidiarity, in favor of a huge, bureaucratic, centralized government. They don't get that this disqualifies them from the git-go.