I think seeing that you don't have anything else negative on your report, and that you did pay it off, it shouldn't be a big issue with an employer.
I recently went through the hiring process, for a casino, and had to get a license, which included an intense background check and credit check, and I'd been unemployed for several months and had gone trhough my savings, I was almost maxed out on my credit card limits. There was one serious error on the credit report they pulled. Collection accounts from the same CA that had been paid in full over five years prior, but had never been reported as paid to TU, and I hadn't caught it, but they did. I sent a dispute letter to TU, I showed the employer a copy of it, as well as going into the office with copies of my other two credit reports that didn't show it, and even though it was a tedious process, it was well worth it (those are now off my report). They even told me they care about revolving credit the most, not how much, but my payment history. They WANT to hire you, that's why they're willing to go through the tedious background checks once they meet the right candidate. You could also just bring up to them first that the AMEX was close to it's limit and you paid it off, that way they see you're an open book.
But, by the way you're describing your history, etc., I think you'll be fine.
