Historically, the FAL is the best NATO battle rifle ever put out. It was widely adopted and is the second most mass produced firearm in the history of the world.
I would not recommend the M1A. During one of my earlier deployments we got a shipment of the M21 DMR conversions in and they were simply awful. They would lose zero after just a few hundred rounds and the barrels would have to be re-headspaced by a master-armorer. On top of that, they just can't keep dust and dirt out of the action. InRangeTV has done a mud-test on the M1A and even a Hi-Point C9 fared better. It had the shortest service life in American history of any rifle and it only got the job over the T-48 (FAL) by rampant corruption and cheating by the Ordnance Department which was so prolific that in 1963 the entire department was shuddered because of it.
G3s are nice rifles but the ergos are antiquated, and it shows, plus the delayed recoil takes practice getting used to.
Practically speaking, things change a lot in modern times in America.
M1A still isn't a consideration because the flaws are simply intrinsic to the design. Doesn't matter how nice it is.
FALs also get mostly ruled out due to the only domestic manufacturer, DS Arms, having a LONG history of horrendous quality control issues plus the cost is considerable. You're looking at $2k plus more to modernize it with better ergos, rail mounts, MLOK handguard, et cetera. DS Arms does offered modernized versions but they're very pricey. There are still great kits out there and some fantastic gunsmiths like Gunplumber of Arizona Response Systems who can build a flawless FAL or fix any issue with a DS Arms rifle but it's gonna cost ya. Plus new, good quality steel mags run $30/per and even average surplus mags are over $20.
Which brings us to the G3. PTR makes a fantastic G3. The build is excellent, their quality control is excellent, and you can get models that are as modernized as the pattern can really get. Plus surplus mags are dirt cheap, I've seen them as low as $1 on even big sites, and new mags are also cheap. Oh, and it's a $900 rifle making it, by some margin, the cheapest option.
So, yeah. The FAL is the best historically but when it comes to domestically produced guns PTR is a far better company than DSA so the PTR-91 wins this argument unless you're ready to hand $3k to Gunplumber for the best of the best.
Sidenote on AR-10s, I've never seen one complete a match without a malf. YMMV.