I am a former competitive swimmer, having trained for 10 years at 20 hours a week, but I recently transitioned to cycling about four months ago. I bought my first road bike, a Trek Domane AL2 Gen 4, and have invested in all the necessary gear such as jerseys, bibs, shoes, etc. I raced in two triathlons, one the day after I bought the bike, and another in which I placed second in the U19 age group and 35th overall out of about 300 men. I’m also running on my high school cross-country team. I enjoy tri but I specifically have a passion for cycling.

According to my family’s Peloton stationary bike, my FTP is around 240 watts. While maintaining a zone 2 heart rate, I can average around 20-21 MPH on flat routes for 40-70 miles. I’m curious about the realistic future I might have in cycling, especially with a strong interest in crit racing. I would also love to compete in stage races and tours. Also, any general tips or training advice to help me improve would be greatly appreciated.

Find a local cycling club and ride in the groups. Start with the slower folks and move up as you get used to riding in a group. Learn the protocols of group riding, taking pulls, pulling off, etc….. group riding always makes you faster as you have to respond to others, at movements when you feel like you want to slow down, etc…,

Practice doing ”bricks” which are the quick transitions from the bike to the run, it gets your legs adjusted to the different muscle uses. In other words, after you’ve done a 40-50 mile hard group ride, throw on your running shoes and go do a 5 mile run.

Welcome aboard, @bbuffalo! That's an impressive background in swimming and a fantastic start in cycling.

Hopefully there is a club/team in your area that you can join and start learning 'racing skills'...they are far different from 'tri skills'...handling, positioning, control, etc.
How far you can go depends on a lot of variables ie, how old are you? Do you live in a 'racing area'? How willing are you to put in the time, energy and effort to achieve higher levels?
In general it starts with training and practice...especially if you are interested in crit racing...it is a very different element of racing and requires a lot of different skills rather than 'just' strength.
You will need a USAC racing license and will likely start as a category five racer...you upgrade the beginning levels based on how many races you participate in so you can generally go from cat 5 to cat 4 to maybe cat 3 in one season depending on how many races you do and how well you place.
Expect to get your head handed to you in the first few races...crits start at 'full gas' for the first few laps in order to 'burn off the dead wood' making it safer for the remaining. The USAC official may pull those 'dead wood' riders off the course as a matter of safety so don't get angry when it happens to you...it happens to everyone when starting and it is a learning opportunity.
Crit racing demands repeated full gas efforts generally lasting around 30 seconds so blocks of 30 seconds on/off intervals at full gas is a very useful training regimen.
There is so much more...the general rule of thumb is it takes 3-5 years for a beginner to become a competent racer.

If you expect to make money as a bike racer in the states...keep you day job. Racing isn't big in the states and the pro teams riders aren't getting big money to race...that happens in Europe.

What are your hopes, expectations, etc.? Where do you live? Buffalo NY? that is a good area for racing.

you’re already ahead of the game with your swimming - anyone with good knees can learn to run effectively - the technique isn’t hard, and cycling is even easier - get a decent bike and start putting in miles. Swimming at a competitive level takes years of training and development, both physically and technically.
My daughter, who swam competitively through high school, entered a sprint triathlon (IIRC 750 yd open water swim, 14 mi bike, 3 mi run) just to try it out. She’s no runner, and she sat on a drop-bar bike for the first time two weeks before the event (and crashed her first time out &#128580. She was in a field of several hundred women, ranging from first-timers like her, to gaunt single-digit-body-fat « serious triathletes ». She managed to completely stuff the transitions. In the end, she finished lower mid-range, but her swimming leg time was 7th overall, regardless of age group. With a couple of years work, she could have become a competent runner and cyclist, but she’s been competing in the water from the age of ~6 - no amount of adult « putting in the miles » in the pool will compete with that

Given all you've noted above.- you should move as quickly as possible to becoming integrated into the competitive community of cycling (if that is what you want to give at try at.
1. Join a Racing club - not any club, a racing club
if you're not familiar with those in your area, go to a highend bike shop, and ask. Ask around until you get references
For us to give good references to what you're asking, we need to know where you are. The more specific you can get as to Town/City, the better we can help get you pointed in a good direction.
Here in the Santa Barbara area, my club has a junior development program - most areas with strong cycling competition and clubs will have that.
2. You will need to join USA Cycling - the governing body for most cycle racing in the US .... I recommend waiting to join until you settle onto a club you wish to affiliate with.
But do go to their website to become familiar with their resources.
3. There are 'Teams' also, outside of the club structure, but that's harder, more time consuming to get acquainted with, start with a strong racing club.
4. Training - no one on here is going to be able to give you a good training program - fragmented 'Tips' are not helpful... Best is initial in-person work.
5. don;t worry about equipment until you do all of the above.

Maybe ask the Moderators here at Bike forums to move this/your thread to the Racing Sub-forum of Road forum - or post the same message there, if you want to have comments from both areas.

It's REALLY important to know where you are. At 19 you should move as quickly as possible to do the above and become strongly integrated into the bike racing community.
Bike Racing is a wonderful thing, for some of us... and can be a lifelong thing... You never know how far you can go with it (or anything) until you try...

I, and I'm sure others here, will be very interested in your progress, so please don;t be a stranger, drop by and let us know how things are going!
Ride On
Yuri

EDIT: Haven't been on USA Cycling for some time - They have a lot of resources - Finding an affiliated club, getting started, etc - definitely worth working through the site. But direct contact in your area is very important.

I don't know, (I think we have a Training subforum that might be more appropriate?) but I love that there are still young people who are willing to work hard to pedal a bike.