The justifiable size can't be quantized too easily. Perhaps technology automation should have brought it down further but it is still not as high compared to competing economies. The EU for example has a tiny equivalent of the US' federal government but in all forms down to local level as much as 18 percent of Europeans in 2022 were "government" in one form or another. The all US figure will across states will be a significant percentage but not as high I am confident.