Growing American Innovation Now Act This bill modifies terminology for purposes of the New Source Review (NSR) permitting program of the Environmental Protection Agency (EPA). In order for a change to a stationary source to be a modification (a change to a stationary source that increases the air pollutant emissions or results in new pollutants) for purposes of the NSR permitting program, the maximum hourly emission rate achievable by such source must be higher than the maximum hourly rate achievable by such source during any hour in the 10-year period preceding the change. A change at a stationary source is not considered to be a modification under the bill if it is designed to (1) reduce the amount of any air pollutant emitted; or (2) restore, maintain, or improve the reliability of operations at, or safety of, the source. However, such changes are not excepted if the EPA determines the increase in the maximum achievable hourly emission rate from such change would cause an adverse effect on human health or the environment. Construction for a major emitting facility (a type of stationary source) does not include a change at such a facility that does not result in a significant emissions increase or a significant net emissions increase. In relation to major emitting facilities in nonattainment areas, the terms modifications and modified do not include changes at such facilities that do not result in a significant emissions increase or a significant net emissions increase.