Tony:

Thank you very much for pointing that out, I did not realize that was the case. I'm a Canadian citizen & Canadian resident, hence it is 'reasonably easy' for me to visit our southern neighbor without too many restrictions.

I'll reiterate my previous recommendation to the original poster: Visit a US immigration or border patrol office as soon as possible, explain the problem (needing an extra week), and ask them what they can do to assist. The American government is a bit flakey and overly-authoritative, but when dealing with Americans on a one-on-one basis, they are usually pretty kind and helpful.

For example, I remember once ferrying an aircraft from Canada (Yukon) to Anadyr, Russia. I deliberately planned to overfly Alaska because my co-pilot, an Indonesian, did not have a USA visa. The weather turned rotten in Anadyr and I had to turn around and divert to Nome, Alaska. I asked Flight Service to call US Immigration and tell them I was landing in Nome with a person who did not have a visa. When the immigration officer arrived, he was extraordinarily friendly and understanding... he said it was obvious that I did not plan to land in Nome, and that as long as we left the next day (weather permitting), there would be no problem at all. He then stamped us both into the country and wished us a good time.

The key to that success, I think, was that I notified Immigration in advance (by radio) of the problem.

Michael