Attempt to sail a beneteau 21.7 across the atlantic?

Wow! Those little suckers are cool. Kind of like a trans-atlantic Laser. Not for me today but at one time I would have been tempted.

What about this guy?
Hungarian sailing around the world in a tiny yacht at Yacht Haven Marina - YouTube

No problems with size or speed, but a pivoting keel would worry me ............ Google 'Plumbelly' to see what you can sail around the world in sucessfully.
And Mini Transats might be designed to sail transatlantic, but in actual fact they're not very easy to sail single handed, so hats off to the folk that race them.

I hope you realize that you (should have) answered your own question. No matter what size boat you want to sail across the Atlantic, you, my good person, are nowhere qualified for it. Your admitted lack of experience should have put the brakes on this thought. Taking lessons and chartering may be a good start, but even then, boat and captain may still not be ready.
Why am I so hard on this (and not just on k8 but any other person with unprepared ambition)? Because when you run into an issue, your problem now becomes other people's problem, like the Coast Guard from the closest country that has to come out and bail your ars out of a situation you should never had gotten into int he first place. Or perhaps a merchant ship that has to change course to look for a dot on the horizon. Too many people think they can do things like this only to find out that the can't, while in the middle of doing it.
Now let me get back to my brain surgery. Well, I own a scalpel so I should be able to do it, right?

... perfect response to a lot of the "newbie" questions ...

I own a scalple and can do brain surgery... but i don't expect the patient to live during or after...
As for stupid questions from newbies... If you never ask you will never learn anything... All questions from novices should be asked so they learn the right answers, I have been told so much garbage from land captains and come to this site to learn the facts.

I am thinking about the same thing sailing a small boat across oceans and the professionals here have advised me to go larger than 25ft (our intended first boat) when you think about all the supplies and everything you have to carry and how the boat will handle under all this weight... every extra foot is a blessing and more stable.

we are looking for something in the 30 to 40ft range with a steel hull as it is still small, hold alot more supplies and alot more forgiving than wood or fibreglass, if/when you make a mistake (& everyone will make mistakes even professionals from time to time).

While we can set sail today with my boat licence, this would be stupidity, we intend getting training and sailing first in lakes, then around the coast of australia, after this we will sail the short jumps to PNG and NZ, then the roaring forties to tassy....

Only after we do this, we will then assess our skills and maybe set off around the world... to be honest i dont see us leaving for 3-5 years.

Dont get discouraged by any posts, but dont just jump in either...
all good things take time, and to do them safely takes just a little longer.

I mean this in the kindest of terms, but if you do not have any blue water sailing experience, you do not belong an a 22 foot boat in the middle of the atlantic. At least crew on a couple of transatlantics to get a sense of what you will incurr out there