The Democratic Party became affiliated with a social-democratic int'l?

[The Mikado]

With a few exceptions, nothing on the list of parties that are members of that organization are particularly radical. There's even parties that are arguably to the Democrats' right, like whatever the hell the Italian Democratic Party is now (given that it now encompasses everything from the far left to center right of the Italian political spectrum).

[Famous Mortimer]

Progressive Alliance is not explicitly social democratic, it just includes social democrats.