I don't know the details of the technological differences in transaction communication between the two, but in the UK chip and pin is noticeably and consistently faster to perform transactions in my experience, often to the the point that it's perceptibly instant... although it has been quite some years since i've used magnetic ones so that's from memory.
I suppose one way to protect yourself if you are never going to use your card in the US, is by destroying the magnetic strip (magnetically).
Most of the machines were replaced inside of the first year and things have improved substantially since then.
* many places moved from offline magstripe authorisation to online chip-and-pin authorisation (while still often using card terminals that use dialup connections, and connect per transaction)
* many US banks have really slow authorisation servers (for whatever reasons!); I remember some sales staff being really surprised at my card going through in about a second (and that verification probably involved a network roundtrip to the UK!)
I don't think the percieved speed is simply due to offline mode.
Also, I don't think there are any places left where you swipe the magnetic stripe. If for some reason you don't use contactless, it's a chip transaction. I believe it's pretty much the same all across Europe?
Just swipe it three or five or more times, and it might work anyway.
Welcome to the 21st Century.
When I'm at O'Reilly Auto Parts, the pinpad is beeping at me to remove my card almost the moment I've inserted it. It's shockingly fast. (Then their neolithic-age printer takes 8 more seconds to generate a receipt, but... baby steps!)
I wish whoever set up their system could go show some others how it's done. Because yes, on average, most retailers have abominably slow processing for chip cards.