That is simply not true. There are lawsuits about this all the time particularly having to do with filming Military installations, it's a first amendment issue. It is not illegal to film in public in the U.S.. There is no expectation of privacy in public. However, private property owners have the right to ban filming on their property. Aside from that and I guess "upskirting" that Amy mentioned it is not illegal to film in public. However, if you're going to use the images/video for commercial gain such as in advertising you must get a waiver. Places like Disney land likely post notices so that they can legally use images for commercial advertising purposes.
http://schoolvideonews.com/Legal/When-is-it-Legal-to-Film-People-Without-Their-Permission
https://www.rocketlawyer.com/blog/ask-a-lawyer-filming-in-a-public-space-97747