TGUS keeps on getting better and better. Season three was great, and so far season four has been downright awesome. Sadly, the same cannot be said for the mothership.
These days, I look forward to TGUSA more than TGUK. The mothership has lost its lustre,
1 - The hosts don't seem to have that same relationship as TGUK. I think that is portrayed mainly in TGUS's lack of a sit down News type segment where TGUK typically take some time to riff on each other and kind of show that even off camera they spend time together as friends instead of just as co-workers. I don't get that sense from TGUS, so their banter kind of appears to be forced or rehearsed.
Go watch an early episode of TGUK. By early, I mean Series 2-early (as James was not in the first series). The chemistry between Jeremy, James, and Richard at that time was very stilted. IMO, they didn't gel as a trio until around Series 4. On the other hand, Adam, Tanner and Rutledge (IMO) started gelling with the first Alaska special, at the end of US S1. They did in nine episodes what it took the UK trio twenty to thirty to do.
You also need to remember that the US is a larger country than the UK, and that all three US hosts have established careers outside TG. Adam has his stand-up and acting. Tanner has his racing. Rutledge covers NASCAR (and is a father to two young girls).
2 - TGUS doesn't seem to do many car reviews. TGUK's opinion on a car actually seems to be a big deal over there (See the Stig crashing a koenigsegg, saying it needs a wing, and then the company adding a wing and sending it back to TGUK. Also see Rover refusing to give TGUK a car to review, resulting in James May's secret mission review. Also see Chrysler refusing to give Hammond a Challenger during one of their runs through the US). I get the feeling that car companies across the pond either look forward to TGUK's review, or look to TGUK's complaints to further improve their cars. TGUK's chief complaint about American cars are 'rubbish interiors', and I tend to agree. I think if serious motoring journalists started being vocal about plastic not belonging on the interior of a 'luxury car', our own auto companies would start producing better products that TGUK might actually start paying attention to. I don't think TGUS has that kind of fan base to influence car makers though.
TGUSA
did do car reviews in the first season. They scrapped it in favour of the challenges because they were more popular. And besides that, IMO, the reviews weren't really necessary. If someone in the US wants to see/read a car review, there are plenty of other places to look. (e.g., Car & Driver, Motortrend, Consumer Reports)
3 - All of TGUS seems like specials or challenges. This again seems to be due to a lack of a news segment, car review segments, or celebrity interviews to break up the main feature. Additionally, TGUS's challenges don't look like the presenters actually took part in the challenge aside from driving the creations. For example - the Alaska convertible challenge - do you think any of the presenters actually built their convertibles? As crappy as they were, it looks like a lot of time was actually spent in a shop with real metal workers and fabricators. TGUK gives the impression that the presenters actually do a lot of their own fabrication on their challenges, and the end product usually reflects that in a far more humorous way.
S1 had an occasional news segment, and the first season and the first half of Season 2 had "Big Star, Small Car" (SIARPC).
I still maintain that -- given their filming schedule at El Toro at the time (two weeks to film all the studio links, plus BSSC) -- a proper news segment was impossible to do. By the time the episodes aired, virtually any news would be redundant. If they filmed similarly to the UK guys -- e.g., filming at El Toro on a Thursday or Friday to air the following Tuesday -- it would be different.
4 - TGUS seems to exist in a vacuum where TGUK doesn't exist. TGAUS went bust, but at least they did tie ins with TGUK and followed the format, even opened with Jessica. There was a feeling that all was right in the world. TGUS doing its own opening music, never mentioning TGUK, having a Stig character but only so rarely seeing him utilized (Though fairly pointless because isn't Tanner actually an accomplished rally driver?), it just seems like the Stig was there only attempt at paying tribute to TGUK and he seems to have been retired. As it is now, I don't see much reason for TGUS to carry the Top Gear brand since it has so little to do with the Top Gear that the world already knows. It could just as well be called Shenanigans with Cars.
Season 1 had the "Jessica"-based theme. It was ditched. IMO, it
was to separate itself from the mothership and forge its own identity, which I believe was the right thing to do, and this is why I think TG Australia failed.
It seems less genuine now than it did in its heyday. While the guys still enjoy each other, enjoy working together, whatever the show had is practically diminished because a lot of it is so damn contrived within an inch of its life that it doesn't seem natural at all. I barely watched UK S20 (only saw two episodes) because S19 was just so lacklustre after the very stellar S18, that I got sick of having to endure the rollercoaster. I honestly don't know if I'm going to bother with this year's Christmas special or Series 21.
On the other hand, I'm much more eager to see what Adam, Tanner, and Rutledge are going to do next. I loved last week's US episode. Best Top Gear episode I've seen, from either franchise, in the last three years.