Surely only a legend, manufactured by an obscure self-called historian.

The legend say that Ney had managed to escape to the United States, using his Masonic ties, including the Duke of Wellington, who helped him fake his execution and flee abroad. The soldiers in the firing squad would have put blood packets over his heart and then shot blanks at the Marshal, after which he was smuggled to the United States, where continued his life as a school teacher under the name of Peter Stuart Ney, and where he would have died in 1846, reportedly after uttering those final words, "Bessières is dead; the Old Guard is dead; now, please, let me die."
On his gravestone in Cleveland, North Carolina, at Third Creek Presbyterian Church on Third Creek Church Road, one will find the words "(...) soldier of the French Revolution under Napoleon Bonaparte (...)."

Fact is that this legend cannot be proven, as long as his corpse, which is buried at he Lachaise Cimetery in Paris, is not excavated to take some DNA to match with other DNA, preserved in the Ney family and to match with the DNA of the body in the US.
And there isn't any artefact left to prove this legend, other than that gravestone.

Fact is also that he betrayed King Louis XVIII to which he pledged his allegiance after the abdication of Napoleon in 1814, to hold his functions an to become a Pair of France, a fact the king didn't forget. After the second abdication of Napoleon, Ney was detested by almost all French political parties, exception made by the Republicans, who formed a small minority.
Further on, he refused to be tried by the other marshalls (some of which refused to take part in this trial), and asked himself to be tried by his equals, the chambre of Pairs (which were for the most part monarchists), and no less than 128 members voted for his execution. Ney was executed by a French firing squad, commanded by a French officer.

Also in 1831 he was rehabilitated by Louis Philippe 1er, and reintegrated on the lists of the Légion d'honneur.

Element against the legend is the question that the so-called American teacher should never had heard of that rehabilitation and never came back to France, where he would have been rehabilitated also in some function as inspector-general of the army.

The legend was also given some food as in 1903 the 3rd Republique wanted to make a beautiful gravestone for the marshall, which body was buried under a simple stone. On the excavation of the former grave by one worker (?), these would have noticed that it was empty ? fact that wasn't testimoned by some officials.

As my good friend Bruno had already written on this website - quoting him - "The British wanted to see some executions. According to the myth a British officer rode over Ney's corpse. Yet they are the same ones who created the gallant foe imagery of Ney in their Waterloo mythology, elevating him to the "super marshal" group to which he did not really belong. This is where the escape to America story comes in, where Wellington, filled with remorse organizes a mock execution and arranges an escape to the Carolinas. There Ney supposedly became a schoolmaster (Peter Stuart Ney). The same goes for the Masonic lodge escape plot where the execution squad fires blanks, Ney is issued with stage blood and is then rescued by members of the "Ancienne Fraternité" lodge. But Masons as an anti-clerical liberal underground is post-1815. Both stories might do well as Hollywood happy endings, but can be qualified as examples of a typical denial syndrome."

Hope this helps

Marc