Hate to say it man but that's changed DRASTICALLY in the last few years. Herrin's performance will 100% influence fate of (near) future US riders. This isn't speculation. This is fact from talking to the top GP team bosses in GP and Moto2 about American racers, talent, and series.
Does this have to do with them really caring about Herrin's performance, or just risk/reward ratio with regards to future sponsorship? Taking an American is a big risk, I think, just because of a dearth of commercial support for them. Would future sponsors just pass on underwriting Americans? I think the lack of wide marketability for Americans is the biggest issue. Most riders that go into a series will flop, by definition. I'm sure an American with a Toni Elias like career wouldn't have a job in GPs anymore. Does an American have to be pretty much spectacular to be a commercial success over there? JH the younger, the future of America (in road racing) is in your able hands. No pressure!
I would bet the depth of field, politics and money (not necessarily in that order) will still influence, more so.
I've talked to some of them too and they'll always keep looking at the US. What PJ and Tommy have done in the UK, what Joe has done in the rookies cup and what Josh does next year and what Ben did all contribute but I don't see any one single thing happening right now being hugely influential.
The problem with 'mericans outside the US in the past was they were expensive. If they produced, it was money well spent. If they didn't, it ruined the euros and japanese on 'mericans.