Once in Carway US-Canada border I saw a US immigration officer denying entry to a lovely british lady because her Canadian visitor record was expiring in less than 90 days. Also, she was planning to return to Canada using a private plane. The USA officer argument was that she was not providing any proof (like an airplane ticket) that she had the intention to return to Canada before her Canadian visitor record expire. The officer was worried, in other words, that she might stay in the USA 90 days, then not been allowed to enter Canada (because her visitor record was expired) and "stuck" in the States.
My advice, based on this experience, would be to provide the US officer with proofs that you are intending to come back.
