Strictly anecdotal, but I had a job early in my career that used American Funds. I didn't understand much about investing at all, so I had very little invested thank goodness.
Things I learned about them:
Usually used as the investment company option for smaller companies. This is because they get to sell their front loaded funds to the participants (the employees participating), and therefore charge less to the company itself for having a retirement plan. This is a big selling point to the employers that think they are providing a great investment/retirement option for their employees, but it actually is kind of sucky that the employer does this, because they may not understand that there are better options (less costly and better performing funds) plan providers with better investment options (lower expense ratios, no plan fees, etc.). And the suck part is their lack of understanding/laziness in researching plan providers results in making you pay more to invest your own money.
American Funds = lots of front-loaded funds. These are almost across the board horrible, because they skim several percentage points right off the top from your contribution as a fee for just getting to invest. I still don't understand how anyone can justify front or back end loads, and they should be outlawed... especially since they are all managed funds and never perform as well when you take into account the front load, and the expense ratio.
What the rep told you is not unique to them. Most places like them are going to do the "we are so awesome our funds are worth the extra expense and you won't be able to find better so don't even bother looking" in some form or another. It's what they do - they are sales people first and foremost, so they'll continue to try to sell you on their funds and do whatever possible to keep you from leaving.
That being said, I'd try asking your plan administrator (at your company) if they would consider using Vanguard instead of American Funds, and if they don't, just hold your nose and keep investing with them until you change jobs. Because even a stinker of a plan is better than no plan.