Even if same train, it is not run under the same regulations. The US FRA regulations really kneecap the operational speeds:
For the track between New Haven and Boston, [Acela] has a waiver for operation at 7 inches of unbalanced superelevation. This means, that the [tilting] Acela is allowed to use the same curve speed as non-tilting TGVs (or multiple units) in France. The “Acela Express” looses about half an hour between New York and Boston, compared to best practice in tilting train usage. (It also looses at least half an hour, compared to the calculations of US railroad engineers in the 1960s.)
Note that the above was written about Acela 1. The Acela 2 is supposedly lighter weight, so in theory FRA might allow higher speeds (though I have yet to see any progress there).
Even if same train, it is not run under the same regulations. The US FRA regulations really kneecap the operational speeds:
Source: https://zierke.com/shasta_route/pages/15regulation.html
Note that the above was written about Acela 1. The Acela 2 is supposedly lighter weight, so in theory FRA might allow higher speeds (though I have yet to see any progress there).