...Kind of? I still don't think we ever hit lolicon or Papuwa levels before that. The first anime officially released in the US on home video, according to Anime News Network's encyclopedia, was Robotech on VHS in 1987. It took till 1993 until we started to get non-giant robot/non-Family Entertainment released anime, but Legend of the Overfiend was indeed among the first of them. But we got Akira at almost the exact same time.
Which brings me to this thread. I was researching "When did the Anime Bubble burst?" (aka "when did the 'Anime as a phenomenon on TV' end?") and I found this thread. I was trying to pin down the crash of anime on TV to a single month/year. An initial starting thought would be "When Toonami ended in October, 2008", but as others here said, it seems the market had already crashed before then.
I think the signs of the collapse where there starting in 2004 and 2005, but there was still some popular anime bursts (Naruto in 2005/2006 perhaps being the main one). However, "Anime Unleashed" ended on the G4 TV channel in March, 2006. That may have been the moment. But Naruto was still going strong...
Others here referenced the collapse of the "Anime on DVD" market in 2007 (which is tied in with the larger collapse of the DVD market in the later half of the 00's). But I'm looking more for when anime collapsed on TV, not on DVD. And right now, I'm split between two dates:
In September, 2006, Kids WB lost the rights to Pokemon and Yu-Gi-Oh (this was tied in with the month when "The WB" ended and it became "The CW", thus eventually ending "Kids WB").
In March, 2007, Cartoon Network rebranded the Toonami block with a new version of TOM and a new line-up (which was bad). After that, even Naruto went on the decline in popularity.
Someone above in this thread pointed to "Death Note" (which first aired in October, 2007) as the last anime series to obtain American pop culture acclaim, but...I want to say that was a return to anime being a cool niche sub-culture (for people who were like "Death Note's only for the cool people who know it airs late at night")...similar to when anime aired on the niche "Saturday Anime" program on the Sci-Fi Channel back in the 90's. Speaking of the Sci-Fi Channel, "Ani-Mondays" started airing late at night in June, 2007, but that also was a pretty niche/obscure anime programming block.
So yeah. I'm leaning towards September, 2006 or March, 2007 as the point where anime stopped being a mainstream pop culture "thing".