Honestly the exact percentage keeps changing every year and varies by source, so its best to check official health stats for the latest number. From what I read it has actually been declining there over the years.
I dont know the precise figure but I remember reading teen pregnancy rates in the US have dropped a lot over the past decades. For an accurate current percentage I'd look at the CDC data, they publish reliable numbers.
This one is more of a statistics question than a pregnancy care one. The rate has been falling there for years. For the real current number check a proper government health website rather than going by guesses here.
I cant give u an exact percentage beta, that changes year to year. If u need it for a project or report, look it up on an official health stats site, that'll be the correct and updated one.