SELECT "Country" FROM table_72663 WHERE "Margin of victory" = '6 strokes'
What countries have a margin of victory at 6 strokes?
CREATE TABLE table_72663 (
    "Year" real,
    "Dates" text,
    "Champion" text,
    "Country" text,
    "Score" text,
    "To par" text,
    "Margin of victory" text,
    "Purse ( US$ )" real,
    "Winners share" real
)