The phrase "off of" has a long history, which, according to the OED, stretches back roughly 500 years. If you want to consider it to be "wrong", then it certainly has a lot of staying power. Here are their quotations using "off of":
?c1450 in G. Müller Aus mittelengl.
Medizintexten (1929) 116 Take a
sponfull of e licour..of of e fyir and
sette it in good place tyl at it be ny
colde, soo as ou mayst suffryn to
holdyn er-in in hand.
SHAKESPEARE Henry VI, Pt. 2 (1623) II.
i. 98 A fall off of [1594 Falling off
on] a Tree.
1667 A. MARVELL Corr. in
Wks. (1875) II. 224 The Lords and we
cannot yet get off of the difficultyes
risen betwixt us.
1678 J. BUNYAN
Pilgrim's Progress 49 About a furlong
off of the Porters Lodge.
STEELE Spectator No. 306. 6, I could
not keep my Eyes off of her.
DEFOE Mem. Cavalier 281, I had
perswaded him off of that.
RICHARDSON Clarissa V. xiii. 132
Biting my lip, [was to indicate] Get
off of that, as fast as possible.
P. OLIVER in T. Hutchinson's Diary 7
Dec. I. 581 A Rebell
Pirate..taken..off of Cape Ann.
in F. J. Child Eng. & Sc. Pop. Ballads
(1894) V. IX. 106/2 Aff o the weather
[read wether] he took the skin, An
rowt his bonny lady in.
1824 J. WIGHT
Mornings at Bow St. 21 Two young
men..were charged by a watchman with
having ‘bother'd him on his bate,’ and
refused to ‘go along off of it when he
1843 T. C. HALIBURTON
Attaché 1st Ser. II. xii. 210 The
groom has stole her oats, forgot to
give her water, and let her make a
supper sometimes off of her nasty,
mouldy, filthy beddin'.
Clock Alm. in Leeds Mercury Weekly
Suppl. (1895) 5 Oct., He connot
forshame To lift up his een off o' th'
1875 P. BROOKS New Starts in
Life viii. 129 If you could have
filled his pockets with gold, and
feasted his hunger off of silver
1884 ‘M. TWAIN’ Adventures
Huckleberry Finn vi. 45 I'd borrow two
or three dollars off of the judge for
1909 G. GREIG Mains's Wooin' 6
He's swallowed the dictionar', min,
an's tryin' to get 'er aff o's
a1922 T. S. ELIOT Waste Land
Drafts (1971) 5 The reputation the
place gets, off of a few barflies.
1962 F. NORMAN Guntz i. 15, I got hold
of this very very old typewriter off
of a friend of mine.
1974 J. STUBBS
Painted Face xxiii. 284 Get off of me,
will you, sir?
1990 B. ROCHE Poor
Beast in Rain II. i. 44, I was hangin'
around here all the time, gettin'
sweet nothin' off of you.
This may perhaps be more common in American English nowadays, but it certainly didn't originate there.