The Spaniard had a difficult start to the weekend in Austin after stopping on the track during the opening of free practice with a suspected water leak.
While Alonso was able to leave, it emerged that Alpine was not convinced he would get through the weekend without risking further trouble.
Speaking about what happened yesterday, Alonso said: “I think it was something on the water system so we had to stop because the engine was running without water at the time.
“They did a good job fixing it and still did a few laps in FP1.”
Before the final tests in Austin, Alpine opted for a brand new power unit.
This means that Alonso will take a new internal combustion engine, turbocharger, MGU-H, MGU-K, energy tank, control electronics and exhaust for qualifying and racing.
With so many additional grid penalties for new components, that means Alonso is automatically given the start of the grid.
Alonso’s engine change comes at a time of the championship when a large number of drivers are taking new engines.
Mercedes’ Valtteri Bottas takes a five-seater grid in Austin after taking on a new internal combustion engine.
This is its sixth ICE of the season, with Mercedes facing a few headaches with the reliability of its turbo hybrid engines.
Question marks remain as to whether or not world champion Lewis Hamilton will be able to reach the end of the campaign without making further changes.
Sebastian Vettel and George Russell also took new Mercedes engines this weekend and will have to start from the back of the grid.
The final grid positions between the trio at the back will be determined by their best qualifying times.