Tu BiShvat (Hebrew for the 15th day of the Hebrew month of Shvat) is the new year of the trees.
Aufruf (pronounced "owf-roof," or more colloquially "oof-roof ") is a German word meaning "calling up" and refers to a synagogue celebration on the Shabbat preceding the wedding.
Yes, Jews always participate fully in the life of the country of which they are citizens. Many congregations include a prayer on behalf of the country in Shabbat services.
As joyous as the holiday is, it is also a time for serious reflection on the duties of a Jew toward their community, particularly in a post-Holocaust world.