You say that Trump was elected democratically. This is not the case, because the Electoral College distributes political power unevenly among the US citizens. Democracy requires equal power. Otherwise, “one person, one vote” is hollow. Even the Republican Party would not have nominated Trump if the pro-Trump and anti-Trump segments of the rank and file of the Republican Party had had equal political power over the nomination. FPTP voting robbed the anti-Trump faction of equal power on a per-person basis.
You say “… the recent democratic elections in Italy brought to power two anti-establishment political parties, Five-Star and Lega (League), that have solid majorities in both houses.” Please explain how two parties can have majorities in both houses. Majority means more than half. Maybe you mean one of those parties has a majority in one house and the other party has the majority in the other house.