They form their own cluster on PCA plots separate from East Asians, whereas Europeans, Near Easterners and West Asians just flow from one to the other. AncestryDNA's White paper gives Amerindians a high recall rate greater than 90%, actually the range is 91% - 99%. Northern China the recall rate is 71%.
I would not call Amerindians a race, but their ancestry is easily detected.
Putting people into racial boxes can be difficult. Amerindians have some similar features to East Asians, which is why they get lumped with them. It an old argument in Biology lumping or splitting different groups based on their characteristics.