Au contraire mon frère The US did not exist prior to the 1700s. Halloween traces its roots back to the ancient Celtic harvest festival of Samhain. Christian influence converted this to the Western Christian All Hollow's Eve, followed by the actual Nov 1 All Saint's Day, followed by Nov 2 All Souls Day.
In the UK Ireland and Scotland celebrate the same as in the USA. In Derry Northern Ireland the festival will draw 100.000 celebrants.
In mainland Europe, countries like Germany, France, Italy, Sweden USA-type activities, public decorations are indeed rare but many adults still attend private costume parties or nightclubs.
Halloween is celebrated heavily in Japan and in Canada it is second only to Christmas.
In other countries it may not be called Halloween but the basic roots are still present, honoring the deceased, caring for their graves. Such as in Mexico's "Dia de los Muertos".
In the Netherlands St. Martin's Day is the harvest festival, end of the growing season, livestock slaughtered, seasonal wine ready, preparations for winter; Laternenumzug the carrying of paper lanterns (USA they became carved gourds) singing of songs door to door for treats ( USA trick or treat); Martinsfeuer community bonfires to keep the cold at bay (Martin cloak?); and finally the Martinsgans roast goose feast