Ok, so there are about 160,000 standard gas stations across the USA.
www.eia.gov
If EV sales goes wild, some of those gas stations will undoubtedly also try to install EV charging.
Even if it takes 2x or 3x as long to charge an EV, as refilling a gas guzzler, the number of stations will be vastly reduced. Over 90% of the recharging will be done at home, with that remaining 10% for people doing long drives. And as ranges are expanded, that number goes down quite a bit. What proportion of the average American's trips are in excess of say 300 miles total?
Part of the question will be whether we eventually settle on cars like the Fiat 500 and Chevy Spark that had around a 100 mile range, OK for commuting, but horrendous for road trips (especially if they didn't supercharge). They are cheap. Or, will we tend towards vehicles with around a 400 mile range, which will be good for even moderate road trips?
There is some level of convenience. So having a charger where it is needed. When doing road trips, I do much of my refilling at truck stops. Pilot, Loves, Maverick, etc. Rarely do I venture to the small town stations.
I haven't been to a supercharger yet, but I do anticipate chargers to be installed at restaurants, and motels that cater to travelers.
250 Amp isn't common in the USA. People have been installing 200 Amp for the last 50 years or so, and in some cases 2 x 200 Amp for 400 Amp.
I've been recharging my Azure (Ford) Transit Connect using 110V, 10 Amps or so. Any old extension cord will do, but it takes about 2 days to recharge from a deep discharge.
I can't hardly see it as a blip on my electric bill.
Going to 220V, 30 Amps or so would make a huge difference, and would recharge 6x as fast, so I could do a full recharge overnight.
I don't know if you could swing 30 Amps on your 100 Amp panel. It might be pushing it.
I've got a 28 kWh battery pack on my Transit Connect, and don't like to drop it below 1/4 charge.
The Chevy Hummer has a 205 kWh battery pack. The Silverado EV also has up to a 200 kWh pack. So, it could take over a week to recharge at 110V with a deep discharge. But, only a day or so at 220V, 30A or so.
However, you don't necessarily have to start every day with a full to empty discharge, and recharge. If you are only going 50 miles on a 400 mile battery pack, then recharge some, but you'd be fine with going back out on occasion with a 50% charge.
Now back to your 100 amp panel. There are now smarter chargers.
Your big residential power consumption will be with:
Electric Stove, Electric Hot Water, Electric Heaters, Electric Clothes Dryer. You probably are using Natural Gas for some of those. Nonetheless, there will be a time of the night where your power consumption will be minimized. Even with house heat, a smart thermostat would allow you to say set it to 60 degrees at night and 70 degrees in the morning if that is your preference.
So, set your car to charge from midnight to 6 AM. And you may well be fine as long as you don't go bonkers with the charger capacity.
If you have a fixed location where you're working, they could also install chargers for the employees.