Nationalism played an important role in unification in
countries like Italy and Germany because it had helped them free their countries
from different monarchies. Mazzini was able to unify Young Italy after the Fascist movement where members wore black shirts while for Germany,
Garibaldi and his movement wore red.
Central asia I believe idk if i'm correct :/
<span>Church leaders could not agree whether priests should be allowed to get married.</span>
They didn't want the United States to be dragged into another Conflict in Europe should it happen again. and America fell back into isolationism after WW1.
The senate wanted to make some changes to the Treaty of Versailles but wilson didn't allow it, In turn they refused to sign the Treaty. preventing the US joining the League of nations. So we sign our own treaty with the central powers.