Foreign-born naturalized citizens now constitute just over 8% of the US voting population. 
Note that previous research suggests there's typically a lag (depending on english proficiency, education etc.) between naturalization and voting.
California is in a league of its own
Results by state for 2018
Correction: New Jersey (followed by these three other states) are in a league of their own.
In Virginia--home of one of the the recent 'blue' elections--the foreign-born citizen voting population grew by roughly a third between 2014 and 2016/2018.
