If you did that you would only get what the wiring would allow until it overheats and catches on fire, if your panel is large enough you could have it wired to deliver the 30 amps needed but it means running 10 gauge wiring from the panel to your new outlet and you would not be using an extension cord just the trailers umbilical cord. I thought about doing it but for the amount of times we have needed air con it just did not make financial sense for us.
"Well that didn't go as expected"
2015 Chev 2500HD Highcountry Duramax
Cedar Creek Silverback 33IK
Donald&Casey cairn terrier
Rest in Peace Mary my darling wife.
Scottish by birth Canadian by time.