Latest version v255 ready for download in TripleA.

In TripleA
Click Download Maps Button
Click Installed tab
Click 1941 Global Command Decision
Click Remove Button
Click Yes button to remove
Click Ok button (Successfully removed)
Click Close (To force the map list to refresh)
Click Download Maps Button
Find & Click 1941 Global Command Decision
Click Install button (be aware, displayed percentage download is NOT working as intended, have a coffee, it takes minutes to download)
Enjoy!

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v255

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Current v255 documentation, last page has winter turn on instructions.
1941_Global_Command_Decision_Manual.pdf

Suggested minimum stable TripleA version
https://github.com/triplea-game/triplea/releases/tag/2.7.15025
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Link to 1st post that has;
Downloads for new Players
https://forums.triplea-game.org/topic/3326/1941-global-command-decision-official-thread

@RogerCooper THANK YOU

The polygons.txt defines the separate zones to get player-colored (will have a single pixel black border), and the overlay reliefTiles can hide that hard edge border to give the appearance of fully wrapped irregular territories.

@TheDog You can't do it in the xml file. You need to do it in polygons.txt. Here is New Zealand in World War II v3.

New Zealand < (3234,1789) (3234,1789) (3235,1788) (3235,1787) (3236,1786) (3238,1786) (3239,1787) (3239,1791) (3235,1795) (3235,1799) (3236,1800) (3236,1802) (3237,1803) (3238,1803) (3240,1805) (3240,1806) (3242,1806) (3242,1805) (3243,1804) (3248,1804) (3249,1805) (3249,1806) (3251,1808) (3251,1809) (3249,1811) (3249,1813) (3251,1813) (3252,1814) (3256,1814) (3260,1810) (3261,1810) (3262,1811) (3265,1811) (3266,1812) (3266,1817) (3265,1818) (3265,1819) (3264,1820) (3264,1828) (3263,1829) (3219,1829) (3218,1828) (3218,1825) (3219,1824) (3219,1822) (3222,1819) (3222,1803) (3224,1801) (3224,1798) (3226,1796) (3226,1795) (3227,1794) (3229,1794) (3230,1793) (3230,1792) (3231,1791) (3232,1791) (3232,1790) (3233,1789) > < (3289,1698) (3290,1698) (3290,1693) (3288,1691) (3289,1690) (3292,1690) (3293,1691) (3294,1691) (3297,1694) (3298,1694) (3299,1695) (3299,1704) (3300,1705) (3300,1707) (3301,1708) (3302,1708) (3305,1711) (3306,1711) (3308,1713) (3309,1713) (3310,1712) (3313,1712) (3315,1710) (3328,1710) (3330,1712) (3330,1713) (3331,1714) (3331,1719) (3330,1720) (3330,1721) (3329,1722) (3329,1723) (3326,1726) (3325,1726) (3322,1729) (3322,1730) (3321,1731) (3321,1737) (3319,1739) (3319,1742) (3318,1743) (3318,1744) (3317,1745) (3317,1748) (3316,1749) (3315,1749) (3314,1750) (3313,1750) (3312,1751) (3311,1751) (3310,1752) (3309,1752) (3308,1753) (3308,1754) (3307,1755) (3307,1756) (3305,1758) (3304,1758) (3304,1759) (3302,1761) (3302,1780) (3301,1781) (3301,1791) (3298,1794) (3298,1795) (3297,1796) (3296,1796) (3296,1797) (3295,1798) (3295,1811) (3294,1812) (3294,1817) (3292,1819) (3291,1819) (3290,1820) (3289,1820) (3288,1821) (3284,1821) (3283,1820) (3283,1816) (3282,1815) (3280,1815) (3277,1812) (3277,1810) (3276,1810) (3272,1806) (3272,1801) (3273,1800) (3273,1799) (3275,1797) (3275,1795) (3277,1793) (3277,1792) (3278,1791) (3278,1789) (3274,1785) (3274,1783) (3272,1781) (3271,1781) (3269,1779) (3262,1779) (3261,1778) (3260,1778) (3259,1777) (3256,1777) (3255,1776) (3253,1776) (3252,1775) (3251,1775) (3248,1772) (3248,1767) (3249,1766) (3249,1765) (3251,1763) (3252,1763) (3253,1762) (3254,1762) (3254,1760) (3255,1759) (3256,1759) (3261,1754) (3261,1750) (3262,1749) (3262,1748) (3263,1747) (3263,1745) (3264,1744) (3264,1741) (3266,1739) (3266,1738) (3267,1737) (3267,1714) (3266,1713) (3266,1712) (3264,1710) (3264,1709) (3263,1708) (3263,1698) (3262,1697) (3262,1694) (3261,1693) (3261,1692) (3260,1691) (3260,1690) (3259,1689) (3259,1688) (3258,1687) (3258,1685) (3255,1682) (3255,1674) (3252,1671) (3252,1670) (3251,1670) (3249,1668) (3249,1667) (3245,1663) (3245,1662) (3240,1657) (3240,1649) (3239,1648) (3238,1648) (3237,1647) (3236,1647) (3235,1646) (3235,1645) (3233,1643) (3233,1637) (3235,1635) (3237,1635) (3238,1636) (3239,1636) (3240,1637) (3240,1640) (3242,1642) (3250,1642) (3255,1647) (3255,1648) (3258,1651) (3258,1652) (3259,1652) (3266,1659) (3266,1661) (3267,1662) (3267,1663) (3269,1665) (3269,1666) (3271,1668) (3271,1671) (3273,1673) (3273,1674) (3274,1675) (3274,1677) (3276,1679) (3278,1679) (3279,1680) (3279,1682) (3280,1683) (3280,1694) (3281,1695) (3282,1695) (3283,1696) (3283,1697) (3284,1697) (3285,1698) > < (3172,1599) (3172,1599) (3173,1600) (3174,1600) (3180,1606) (3180,1607) (3181,1608) (3182,1608) (3183,1609) (3183,1610) (3185,1612) (3186,1612) (3187,1613) (3189,1613) (3191,1615) (3191,1619) (3189,1621) (3188,1621) (3187,1620) (3185,1620) (3184,1619) (3182,1619) (3180,1617) (3178,1617) (3177,1616) (3175,1616) (3173,1614) (3172,1614) (3170,1612) (3169,1612) (3168,1611) (3168,1610) (3167,1610) (3166,1609) (3165,1609) (3163,1607) (3163,1604) (3162,1603) (3161,1603) (3159,1601) (3157,1601) (3153,1597) (3153,1596) (3157,1592) (3158,1592) (3159,1593) (3161,1593) (3162,1594) (3163,1594) (3165,1596) (3166,1596) (3167,1597) (3168,1597) (3169,1598) (3171,1598) > < (3219,1581) (3220,1581) (3221,1582) (3224,1582) (3228,1586) (3228,1592) (3229,1593) (3229,1594) (3230,1595) (3230,1597) (3229,1598) (3226,1598) (3224,1596) (3223,1596) (3222,1595) (3221,1595) (3220,1594) (3219,1594) (3218,1593) (3218,1592) (3214,1588) (3213,1588) (3212,1587) (3210,1587) (3209,1586) (3209,1578) (3210,1577) (3211,1577) (3212,1576) (3213,1576) (3216,1579) (3216,1580) (3217,1580) (3218,1581) > < (3219,1566) (3223,1566) (3224,1567) (3227,1567) (3228,1568) (3228,1570) (3224,1574) (3222,1574) (3221,1575) (3218,1575) (3214,1571) (3214,1569) (3215,1568) (3216,1568) (3217,1567) (3218,1567) > < (3224,1555) (3226,1555) (3229,1558) (3229,1562) (3228,1563) (3223,1563) (3220,1560) (3220,1558) (3222,1556) (3223,1556) > < (3230,1538) (3230,1538) (3232,1540) (3232,1546) (3231,1547) (3231,1548) (3230,1549) (3230,1550) (3229,1551) (3228,1551) (3226,1553) (3222,1553) (3221,1552) (3221,1551) (3220,1550) (3220,1547) (3222,1545) (3222,1543) (3224,1541) (3224,1537) (3225,1536) (3228,1536) > < (3288,1573) (3289,1573) (3291,1575) (3291,1578) (3288,1581) (3288,1582) (3287,1583) (3284,1583) (3280,1587) (3277,1587) (3276,1586) (3276,1583) (3282,1577) (3282,1576) (3285,1573) > < (3279,1592) (3279,1592) (3279,1591) (3280,1590) (3285,1590) (3289,1594) (3289,1597) (3285,1601) (3283,1601) (3281,1603) (3280,1603) (3280,1604) (3279,1605) (3273,1605) (3272,1604) (3270,1604) (3266,1600) (3266,1599) (3265,1598) (3265,1592) (3266,1591) (3272,1591) (3274,1593) (3277,1593) (3278,1592) >

Note the angle brackets define each particular section.

@GREGOREK

Is there a way to declare two separate territories and then join them so the game treats them as a single territory?

I don't think that is possible. Its the vertical/horizontal map border lines or no wrapping.
Maybe someone else can help?